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1700

In prokaryotes (bacteria and archaea) the situation is more complicated, because there are several different electron donors and several different electron acceptors. The generalized electron transport chain in bacteria is:

Electron transport chain

1701

Note that electrons can enter the chain at three levels: at the level of a dehydrogenase, at the level of the quinone pool, or at the level of a mobile cytochrome electron carrier. These levels correspond to successively more positive redox potentials, or to successively decreased potential differences relative to the terminal electron acceptor. In other words, they correspond to successively smaller Gibbs free energy changes for the overall redox reaction Donor → Acceptor.

Electron transport chain

1702

Individual bacteria use multiple electron transport chains, often simultaneously. Bacteria can use a number of different electron donors, a number of different dehydrogenases, a number of different oxidases and reductases, and a number of different electron acceptors. For example, E. coli (when growing aerobically using glucose as an energy source) uses two different NADH dehydrogenases and two different quinol oxidases, for a total of four different electron transport chains operating simultaneously.

Electron transport chain

1703

A common feature of all electron transport chains is the presence of a proton pump to create a transmembrane proton gradient. Bacterial electron transport chains may contain as many as three proton pumps, like mitochondria, or they may contain only one or two. They always contain at least one proton pump.

Electron transport chain

1704

In the present day biosphere, the most common electron donors are organic molecules. Organisms that use organic molecules as an energy source are called organotrophs. Organotrophs (animals, fungi, protists) and phototrophs (plants and algae) constitute the vast majority of all familiar life forms.

Electron transport chain

1705

Some prokaryotes can use inorganic matter as an energy source. Such an organism is called a lithotroph ("rock-eater"). Inorganic electron donors include hydrogen, carbon monoxide, ammonia, nitrite, sulfur, sulfide, manganese oxide, and ferrous iron. Lithotrophs have been found growing in rock formations thousands of meters below the surface of Earth. Because of their volume of distribution, lithotrophs may actually outnumber organotrophs and phototrophs in our biosphere.

Electron transport chain

1706

The use of inorganic electron donors as an energy source is of particular interest in the study of evolution. This type of metabolism must logically have preceded the use of organic molecules as an energy source.

Electron transport chain

1707

Bacteria can use a number of different electron donors. When organic matter is the energy source, the donor may be NADH or succinate, in which case electrons enter the electron transport chain via NADH dehydrogenase (similar to Complex I in mitochondria) or succinate dehydrogenase (similar to Complex II). Other dehydrogenases may be used to process different energy sources: formate dehydrogenase, lactate dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, H2 dehydrogenase (hydrogenase), etc. Some dehydrogenases are also proton pumps; others funnel electrons into the quinone pool. Most dehydrogenases show induced expression in the bacterial cell in response to metabolic needs triggered by the environment in which the cells grow.[citation needed]

Electron transport chain

1708

Quinones are mobile, lipid-soluble carriers that shuttle electrons (and protons) between large, relatively immobile macromolecular complexes embedded in the membrane. Bacteria use ubiquinone (the same quinone that mitochondria use) and related quinones such as menaquinone. Another name for ubiquinone is Coenzyme Q10.

Electron transport chain

1709

A proton pump is any process that creates a proton gradient across a membrane. Protons can be physically moved across a membrane; this is seen in mitochondrial Complexes I and IV. The same effect can be produced by moving electrons in the opposite direction. The result is the disappearance of a proton from the cytoplasm and the appearance of a proton in the periplasm. Mitochondrial Complex III uses this second type of proton pump, which is mediated by a quinone (the Q cycle).

Electron transport chain

1710

Some dehydrogenases are proton pumps; others are not. Most oxidases and reductases are proton pumps, but some are not. Cytochrome bc1 is a proton pump found in many, but not all, bacteria (it is not found in E. coli). As the name implies, bacterial bc1 is similar to mitochondrial bc1 (Complex III).

Electron transport chain

1711

Proton pumps are the heart of the electron transport process. They produce the transmembrane electrochemical gradient that enables ATP Synthase to synthesize ATP.

Electron transport chain

1712

Cytochromes are pigments that contain iron. They are found in two very different environments.

Electron transport chain

1713

Some cytochromes are water-soluble carriers that shuttle electrons to and from large, immobile macromolecular structures imbedded in the membrane. The mobile cytochrome electron carrier in mitochondria is cytochrome c. Bacteria use a number of different mobile cytochrome electron carriers.

Electron transport chain

1714

Other cytochromes are found within macromolecules such as Complex III and Complex IV. They also function as electron carriers, but in a very different, intramolecular, solid-state environment.

Electron transport chain

1715

Electrons may enter an electron transport chain at the level of a mobile cytochrome or quinone carrier. For example, electrons from inorganic electron donors (nitrite, ferrous iron, etc.) enter the electron transport chain at the cytochrome level. When electrons enter at a redox level greater than NADH, the electron transport chain must operate in reverse to produce this necessary, higher-energy molecule.

Electron transport chain

1716

When bacteria grow in aerobic environments, the terminal electron acceptor (O2) is reduced to water by an enzyme called an oxidase. When bacteria grow in anaerobic environments, the terminal electron acceptor is reduced by an enzyme called a reductase.

Electron transport chain

1717

In mitochondria the terminal membrane complex (Complex IV) is cytochrome oxidase. Aerobic bacteria use a number of different terminal oxidases. For example, E. coli does not have a cytochrome oxidase or a bc1 complex. Under aerobic conditions, it uses two different terminal quinol oxidases (both proton pumps) to reduce oxygen to water.

Electron transport chain

1718

Anaerobic bacteria, which do not use oxygen as a terminal electron acceptor, have terminal reductases individualized to their terminal acceptor. For example, E. coli can use fumarate reductase, nitrate reductase, nitrite reductase, DMSO reductase, or trimethylamine-N-oxide reductase, depending on the availability of these acceptors in the environment.

Electron transport chain

1719

Most terminal oxidases and reductases are inducible. They are synthesized by the organism as needed, in response to specific environmental conditions.

Electron transport chain

1720

Just as there are a number of different electron donors (organic matter in organotrophs, inorganic matter in lithotrophs), there are a number of different electron acceptors, both organic and inorganic. If oxygen is available, it is invariably used as the terminal electron acceptor, because it generates the greatest Gibbs free energy change and produces the most energy.[citation needed]

Electron transport chain

1721

In anaerobic environments, different electron acceptors are used, including nitrate, nitrite, ferric iron, sulfate, carbon dioxide, and small organic molecules such as fumarate.

Electron transport chain

1722

Since electron transport chains are redox processes, they can be described as the sum of two redox pairs. For example, the mitochondrial electron transport chain can be described as the sum of the NAD+/NADH redox pair and the O2/H2O redox pair. NADH is the electron donor and O2 is the electron acceptor.

Electron transport chain

1723

Not every donor-acceptor combination is thermodynamically possible. The redox potential of the acceptor must be more positive than the redox potential of the donor. Furthermore, actual environmental conditions may be far different from standard conditions (1 molar concentrations, 1 atm partial pressures, pH = 7), which apply to standard redox potentials. For example, hydrogen-evolving bacteria grow at an ambient partial pressure of hydrogen gas of 10−4 atm. The associated redox reaction, which is thermodynamically favorable in nature, is thermodynamic impossible under "standard" conditions.[citation needed]

Electron transport chain

1724

Bacterial electron transport pathways are, in general, inducible. Depending on their environment, bacteria can synthesize different transmembrane complexes and produce different electron transport chains in their cell membranes. Bacteria select their electron transport chains from a DNA library containing multiple possible dehydrogenases, terminal oxidases and terminal reductases. The situation is often summarized by saying that electron transport chains in bacteria are branched, modular, and inducible.

Electron transport chain

1725

In oxidative phosphorylation, electrons are transferred from a low-energy electron donor (e.g., NADH) to an acceptor (e.g., O2) through an electron transport chain. In photophosphorylation, the energy of sunlight is used to create a high-energy electron donor and an electron acceptor. Electrons are then transferred from the donor to the acceptor through another electron transport chain.

Electron transport chain

1726

Photosynthetic electron transport chains have many similarities to the oxidative chains discussed above. They use mobile, lipid-soluble carriers (quinones) and mobile, water-soluble carriers (cytochromes, etc.). They also contain a proton pump. It is remarkable that the proton pump in all photosynthetic chains resembles mitochondrial Complex III.

Electron transport chain

1727

Photosynthetic electron transport chains are discussed in greater detail in the articles Photophosphorylation, Photosynthesis, Photosynthetic reaction center and Light-dependent reaction.

Electron transport chain

1728

Electron transport chains are redox reactions that transfer electrons from an electron donor to an electron acceptor. The transfer of electrons is coupled to the translocation of protons across a membrane, producing a proton gradient. The proton gradient is used to produce useful work. About 30 work units are produced per electron transport.

Electron transport chain

1729

"Theme from Mission: Impossible" is the theme tune of the TV series Mission: Impossible (1966–1973). The theme was written and composed by Argentine composer Lalo Schifrin and has since gone on to appear in several other works of the Mission: Impossible franchise, including the 1988 TV series, the film series and the video game series. The 1960s version has since been acknowledged as one of TV's greatest theme tunes.[1]

Theme from Mission: Impossible

1730

The theme is written in a 5 4 time signature which Schifrin has jokingly explained as being "for people who have five legs".[2] However, a more likely explanation is that Schifrin started from the Morse Code for M.I. which is dah dah dit dit. If a dit is one beat and a dah is one and a half beats then this gives a bar of five beats exactly matching the underlying rhythm.

Theme from Mission: Impossible

1731

The original single release peaked at No. 41 on the Billboard Hot 100 and 19 on the magazine's Adult Contemporary chart in 1967 (Leonard Nimoy, before playing Paris in Mission Impossible in 1969, also covered the theme two years earlier).[3]

Theme from Mission: Impossible

1732

In 2010, a fictionalized account of Lalo Schifrin's creation of the Mission: Impossible tune was featured in a Lipton TV commercial aired in a number of countries around the world.[4]

Theme from Mission: Impossible

1733

7" Single

Theme from Mission: Impossible

1734

Side A:

Theme from Mission: Impossible

1735

Side B:

Theme from Mission: Impossible

1736

In 1996, the theme was remade by U2 members Adam Clayton and Larry Mullen, Jr. for the soundtrack to the film.

Theme from Mission: Impossible

1737

It became a hit in the United States, peaking at No. 7 on the Billboard Hot 100 and receiving a gold certification, selling 500,000 copies there.[5][6] It also peaked at number 7 on the UK Singles Chart and at number 1 in Iceland.

Theme from Mission: Impossible

1738

The Gavin Report wrote about the song: "Those not familiar wiith this piece of music A) are under five years of age, B) have been living with Theodore Kaczynski for the past 25 years, or C) are not aware of television. This interpretation by half of U2 will he heard by millions of moviegoers expected to see what's been anticipated as the film of the summer. Try cranking this up and driving around the hills of San Francisco! Very cool."[7]

Theme from Mission: Impossible

1739

One cover version was recorded by French No Wave artist Lizzy Mercier Descloux on her 1979 album, Press Color.[12]

Theme from Mission: Impossible

1740

The theme's melodies form the basis of Limp Bizkit's 2000 single "Take A Look Around", which was recorded for the soundtrack of the second film.

Theme from Mission: Impossible

1741

Russian ethnic band Bugotak recorded a Russian-language rap song with ethnic Siberian instruments based on "Take a Look Around", the theme and "Empty Spaces" by Pink Floyd, entitled "Missiya Maadai-kara nevypolnima".

Theme from Mission: Impossible

1742

Brave Combo covered the theme as a "deep groove cumbia" on their 2008 album, The Exotic Rocking Life.

Theme from Mission: Impossible

1743

In January 2013, violinist and dancer Lindsey Stirling and The Piano Guys, Steven Sharp Nelson (cello) and Jon Schmidt (piano), released their interpretation of the "Theme from Mission: Impossible".[13][14] The arrangement is true to the Lalo Schifrin original, but also employs a passage with a liberal use of the Piano Sonato in C by Wolfgang Amadeus Mozart K. 545 first movement and a self-composed passage to end the piece.[15] The arrangement was introduced with a music video having a comedic cloak and dagger theme. Two official copies of the video have garnered nearly 5 million views on Lindsey Stirling's YouTube channel [16] and over 10 million views on The Piano Guys YouTube channel as of August 2015.[15]

Theme from Mission: Impossible

1744

The navel (clinically known as the umbilicus, colloquially known as the belly button, or tummy button) is a hollowed or sometimes raised area on the abdomen at the attachment site of the umbilical cord.[1] All placental mammals have a navel.[2]

Navel

1745

The umbilicus is used to visually separate the abdomen into quadrants.[3]

Navel

1746

The umbilicus is a prominent mark on the abdomen, with its position being relatively consistent among humans. The skin around the waist at the level of the umbilicus is supplied by the tenth thoracic spinal nerve (T10 dermatome). The umbilicus itself typically lies at a vertical level corresponding to the junction between the L3 and L4 vertebrae,[4] with a normal variation among people between the L3 and L5 vertebrae.[5]

Navel

1747

Parts of the navel include the "umbilical tip", which is the center of the navel often described as a button shape. The "periumbilical skin" surrounds it.[6] Navels consisting of the umbilical tip protruding past the periumbilical skin have been nicknamed "outies". Outies are often mistaken for umbilical hernias, but are actually a completely different shape with no health concern, unlike an umbilical hernia. The navel (specifically abdominal wall) would be considered an umbilical hernia if the protrusion was 5 centimeters or more. The total diameter of an umbilical hernia is usually 10 centimeters.[6] Navels that are concave are nicknamed "innies".[7] While the shape of the human navel may be affected by long term changes to diet and exercise, unexpected change in shape may be the result of ascites.[8]

Navel

1748

In addition to change in shape being a possible side effect from ascites and umbilical hernias, the navel can be involved in umbilical sinus or fistula, which in rare cases can lead to menstrual or fecal discharge from the navel. Menstrual discharge from the umbilicus is a rare disorder associated with umbilical endometriosis.[9][10]

Navel

1749

To minimize scarring, the navel is a recommended site of incision for various surgeries, including transgastric appendicectomy,[13] gall bladder surgery,[14] and the umbilicoplasty[15] procedure itself.

Navel

1750

Abdominal thrusts is a first aid method of dislodging an object stuck in the throat, and is performed just above the navel.[16]

Navel

1751

The public exposure of the male and female midriff and bare navel has been taboo at times in Western cultures, being considered immodest or indecent. It was banned in some jurisdictions, but community perceptions have changed, and exposure of female midriff and navel is more accepted today. In some societies or contexts, it is both fashionable and common, though not without its critics.[17]

Navel

1752

While the West was relatively resistant to midriff-baring clothing until the 1980s, it has long been a fashion with Indian women.[18] The Japanese have long had a special regard for the navel. During the early Jomon period in northern Japan, three small balls indicating the breasts and navel were pasted onto flat clay objects to represent the female body. The navel was exaggerated in size, informed by the belief that the navel symbolizes the center where life begins.[19]

Navel

1753

A microscope slide is a thin flat piece of glass, typically 75 by 26 mm (3 by 1 inches) and about 1 mm thick, used to hold objects for examination under a microscope. Typically the object is mounted (secured) on the slide, and then both are inserted together in the microscope for viewing. This arrangement allows several slide-mounted objects to be quickly inserted and removed from the microscope, labeled, transported, and stored in appropriate slide cases or folders.

Microscope slide

1754

Microscope slides are often used together with a cover slip or cover glass, a smaller and thinner sheet of glass that is placed over the specimen. Slides are held in place on the microscope's stage by slide clips, slide clamps or a cross-table which is used to achieve precise, remote movement of the slide upon the microscope's stage (such as in an automated / computer operated system, or where touching the slide with fingers is inappropriate either due to the risk of contamination or lack of precision)

Microscope slide

1755

The origin of the concept was pieces of ivory or bone, containing specimens held between disks of transparent mica, that would slide into the gap between the stage and the objective.[1] These "sliders" were popular in Victorian England until the Royal Microscopical Society introduced the standardized glass microscope slide.[2]

Microscope slide

1756

A standard microscope slide measures about 75 mm by 25 mm (3″ by 1″) and is about 1 mm thick. A range of other sizes are available for various special purposes, such as 75 x 50 mm and for geological use, 46 x 27 mm for petrographic studies, and 48 x 28 mm for thin sections. Slides are usually made of common glass and their edges are often finely ground or polished.

Microscope slide

1757

Microscope slides are usually made of optical quality glass, such as soda lime glass or borosilicate glass, but specialty plastics are also used. Fused quartz slides are often used when ultraviolet transparency is important, e.g. in fluorescence microscopy.[3][4]

Microscope slide

1758

While plain slides are the most common, there are several specialized types. A concavity slide or cavity slide has one or more shallow depressions ("wells"), designed to hold slightly thicker objects, and certain samples such as liquids and tissue cultures.[5] Slides may have rounded corners for increased safety or robustness, or a cut-off corner for use with a slide clamp or cross-table, where the slide is secured by a spring-loaded curved arm contacting one corner, forcing the opposing corner of the slide against a right angled arm which does not move. If this system were used with a slide which did not incorporate these cut-off corners, the corners would chip and the slide could shatter.[5]

Microscope slide

1759

A graticule slide is marked with a grid of lines (for example, a 1 mm grid) that allows the size of objects seen under magnification to be easily estimated and provides reference areas for counting minute objects. Sometimes one square of the grid will itself be subdivided into a finer grid. Slides for specialized applications, such as hemocytometers for cell counting, may have various reservoirs, channels and barriers etched or ground on their upper surface.[6] Various permanent markings or masks may be printed, sand-blasted, or deposited on the surface by the manufacturer, usually with inert materials such as PTFE.[7]

Microscope slide

1760

Some slides have a frosted or enamel-coated area at one end, for labeling with a pencil or pen.[5] Slides may have special coatings applied by the manufacturer, e.g. for chemical inertness or enhanced cell adhesion. The coating may have a permanent electric charge to hold thin or powdery samples. Common coatings include poly-L-lysine, silanes, epoxy resins,[5][7] or even gold.[8]

Microscope slide

1761

The mounting of specimens on microscope slides is often critical for successful viewing. The problem has been given much attention in the last two centuries and is a well-developed area with many specialized and sometimes quite sophisticated techniques.

Microscope slide

1762

In a dry mount, the simplest kind of mounting, the object is merely placed on the slide. A cover slip may be placed on top to protect the specimen and the microscope's objective and to keep the specimen still and pressed flat. This mounting can be successfully used for viewing specimens like pollen, feathers, hairs, etc. It is also used to examine particles caught in transparent membrane filters (e.g., in analysis of airborne dust).

Microscope slide

1763

In a wet mount, the specimen is placed in a drop of water or other liquid held between the slide and the cover slip by surface tension. This method is commonly used, for example, to view microscopic organisms that grow in pond water or other liquid media, especially when studying their movement and behavior. Care must be taken to exclude air bubbles that would interfere with the viewing and hamper the organisms' movements. An example of a temporary wet mount is a lactofuchsin mount, which provides both a sample mounting, as well as a fuchsine staining.

Microscope slide

1764

For pathological and biological research, the specimen usually undergoes a complex histological preparation that involves fixing it to prevent decay, removing any water contained in it, replacing the water with paraffin, cutting it into very thin sections using a microtome, placing the sections on a microscope slide, staining the tissue using various stains to reveal specific tissue components, clearing the tissue to render it transparent and covering it with a coverslip and mounting medium.

Microscope slide

1765

Strew mounting describes the production of palynological microscope slides by suspending a concentrated sample in distilled water, placing the samples on a slide, and allowing the water to evaporate.[9]

Microscope slide

1766

The mounting medium is the solution in which the specimen is embedded, generally under a cover glass. Simple liquids like water or glycerol can be considered mounting media, though the term generally refers to compounds that harden into a permanent mount. Popular mounting media include Permount [10], and Hoyer's mounting medium and an alternative glycerine jelly [11] Properties of a good mounting medium include having a refractive index close to that of glass (1.518), non-reactivity with the specimen, stability over time without crystallizing, darkening, or changing refractive index, solubility in the medium the specimen was prepared in (either aqueous or non-polar, such as xylene or toluene), and not causing the specimen stain to fade or leach.[12]

Microscope slide

1767

Popularly used in immunofluorescent cytochemistry where the fluorescence cannot be archived. The temporary storage must be done in a dark moist chamber. Common examples are:

Microscope slide

1768

Used when a permanent mount is required

Microscope slide

1769

In contrast to mounting necessary for glass coverslips, somewhat similar mounting can be done for bulkier specimen preservation in glass containers in museums. However an entirely different type of mounting is done for sample preparation, which can be for biological or nonbiological materials and is further subdivided into "hot"(compressive) and "cold" (castable) type mounting processes.[14][15] Though named "mounting", it is more akin to embedding in histology and should not be confused with the mounting described above. The term mounting in other fields has numerous other meanings.

Microscope slide

1770

The United States Capitol, often called the Capitol Building, is the home of the United States Congress, and the seat of the legislative branch of the U.S. federal government. It sits atop Capitol Hill at the eastern end of the National Mall in Washington, D.C. Though not at the geographic center of the Federal District, the Capitol forms the origin point for the District's street-numbering system and the District's four quadrants.

United States Capitol

1771

The original building was completed in 1800 and was subsequently expanded, particularly with the addition of the massive dome, and expanded chambers for the bicameral legislature, the House of Representatives in the south wing and the Senate in the north wing. Like the principal buildings of the executive and judicial branches, the Capitol is built in a distinctive neoclassical style and has a white exterior. Both its east and west elevations are formally referred to as fronts, though only the east front was intended for the reception of visitors and dignitaries.

United States Capitol

1772

Prior to establishing the nation's capital in Washington, D.C., the United States Congress and its predecessors had met in Philadelphia (Independence Hall and Congress Hall), New York City (Federal Hall), and a number of other locations (York, Pennsylvania; Lancaster, Pennsylvania; Maryland State House in Annapolis, Maryland; and Nassau Hall in Princeton, New Jersey).[2] In September 1774, the First Continental Congress brought together delegates from the colonies in Philadelphia, followed by the Second Continental Congress, which met from May 1775 to March 1781.

United States Capitol

1773

After adopting the Articles of Confederation in York, Pennsylvania, the Congress of the Confederation was formed and convened in Philadelphia from March 1781 until June 1783, when a mob of angry soldiers converged upon Independence Hall, demanding payment for their service during the American Revolutionary War. Congress requested that John Dickinson, the Governor of Pennsylvania, call up the militia to defend Congress from attacks by the protesters. In what became known as the Pennsylvania Mutiny of 1783, Dickinson sympathized with the protesters and refused to remove them from Philadelphia. As a result, Congress was forced to flee to Princeton, New Jersey, on June 21, 1783,[3] and met in Annapolis, Maryland, and Trenton, New Jersey, before ending up in New York City.

United States Capitol

1774

The United States Congress was established upon ratification of the United States Constitution and formally began on March 4, 1789. New York City remained home to Congress until July 1790,[4] when the Residence Act was passed to pave the way for a permanent capital. The decision to locate the capital was contentious, but Alexander Hamilton helped broker a compromise in which the federal government would take on war debt incurred during the American Revolutionary War, in exchange for support from northern states for locating the capital along the Potomac River. As part of the legislation, Philadelphia was chosen as a temporary capital for ten years (until December 1800), until the nation's capital in Washington, D.C., would be ready.[5]

United States Capitol

1775

Pierre (Peter) Charles L'Enfant was given the task of creating the city plan for the new capital city.[6] L'Enfant chose Jenkin's Hill as the site for the "Congress House", with a "grand avenue" (now Pennsylvania Avenue, NW) connecting it with the President's House, and a public space containing a broader "grand avenue" (now the National Mall) stretching westward to the Potomac River (see: L'Enfant Plan).[7][8]

United States Capitol

1776

In reviewing L'Enfant's plan, Thomas Jefferson insisted the legislative building be called the "Capitol" rather than "Congress House".[7] The word "Capitol" comes from Latin and is associated with the Temple of Jupiter Optimus Maximus on Capitoline Hill, one of the seven hills of Rome.[9][10] The connection between the two is not, however, crystal clear.[11] In addition to coming up with a city plan, L'Enfant had been tasked with designing the Capitol and President's House; however, he was dismissed in February 1792 over disagreements with President George Washington and the commissioners, and there were no plans at that point for the Capitol.[12]

United States Capitol

1777

In spring 1792, United States Secretary of State Thomas Jefferson proposed a design competition to solicit designs for the Capitol and the "President's House", and set a four-month deadline. The prize for the competition was $500 and a lot in the Federal City. At least ten individuals submitted designs for the Capitol; however the drawings were regarded as crude and amateurish, reflecting the level of architectural skill present in the United States at the time.[13] The most promising of the submissions was by Stephen Hallet, a trained French architect.[14] However, Hallet's designs were overly fancy, with too much French influence, and were deemed too costly.[15]

United States Capitol

1778

A late entry by amateur architect William Thornton was submitted on January 31, 1793, to much praise for its "Grandeur, Simplicity, and Beauty" by Washington, along with praise from Thomas Jefferson. Thornton was inspired by the east front of the Louvre, as well as the Paris Pantheon for the center portion of the design.[16][17] Thornton's design was officially approved in a letter dated April 5, 1793, from Washington, and Thornton served as the first Architect of the Capitol (and later first Superintendent of the United States Patent Office).[18] In an effort to console Hallet, the commissioners appointed him to review Thornton's plans, develop cost estimates, and serve as superintendent of construction. Hallet proceeded to pick apart and make drastic changes to Thornton's design, which he saw as costly to build and problematic.[19] In July 1793, Jefferson convened a five-member commission, bringing Hallet and Thornton together, along with James Hoban (winning architect of the "President's Palace") to address problems with and revise Thornton's plan. Hallet suggested changes to the floor plan, which could be fitted within the exterior design by Thornton.[20][21] The revised plan was accepted, except that Secretary Jefferson and President Washington insisted on an open recess in the center of the East front, which was part of Thornton's original plan.[22]

United States Capitol

1779

The original design by Thornton was later modified by the famous British-American architects Benjamin Henry Latrobe, Sr., and then Charles Bulfinch.[23] The current cast-iron dome and the House's new southern extension and Senate new northern wing were designed by Thomas U. Walter and August Schoenborn, a German immigrant, in the 1850s,[24] and were completed under the supervision of Edward Clark.[25]

United States Capitol

1780

L'Enfant secured the lease of quarries at Wigginton Island and along Aquia Creek in Virginia for use in the foundations and outer walls of the Capitol in November 1791.[26] Surveying was under way soon after the Jefferson conference plan for the Capitol was accepted.[20] On September 18, 1793, President George Washington, along with eight other Freemasons dressed in masonic regalia, laid the cornerstone, which was made by silversmith Caleb Bentley.[27][28]

United States Capitol

1781

Construction proceeded with Hallet working under supervision of James Hoban, who was also busy working on construction of the "President's House" (also later known as the "Executive Mansion"). Despite the wishes of Jefferson and the President, Hallet went ahead anyway and modified Thornton's design for the East Front and created a square central court that projected from the center, with flanking wings which would house the legislative bodies. Hallet was dismissed by Secretary Jefferson on November 15, 1794.[29] George Hadfield was hired on October 15, 1795, as Superintendent of Construction, but resigned three years later in May 1798, because of his dissatisfaction with Thornton's plan and quality of work done thus far.[30]

United States Capitol

1782

The Senate (north) wing was completed in 1800. The Senate and House shared quarters in the north wing until a temporary wooden pavilion was erected on the future site of the House wing which served for a few years for the Representatives to meet in, until the House of Representatives (south) wing was finally completed in 1811, with a covered wooden temporary walkway connecting the two wings with the Congressional chambers where the future center section with rotunda and dome would someday rise. However, the House of Representatives moved early into their House wing in 1807. Though the Senate wing building was incomplete, the Capitol held its first session of the United States Congress with both chambers in session on November 17, 1800. The National Legislature was moved to Washington prematurely, at the urging of President John Adams, in hopes of securing enough Southern votes in the Electoral College to be re-elected for a second term as President.[31]

United States Capitol

1783

For several decades, beginning when the federal government moved to Washington in the fall of 1800, the Capitol building was used for Sunday religious services as well as for governmental functions. The first services were conducted in the "hall" of the House in the north wing of the building. In 1801 the House moved to temporary quarters in the south wing, called the "Oven," which it vacated in 1804, returning to the north wing for three years. Then, from 1807 to 1857, they were held in the then-House Chamber (now called Statuary Hall). When held in the House chamber, the Speaker's podium was used as the preacher's pulpit. According to the U.S. Library of Congress exhibit Religion and the Founding of the American Republic:

United States Capitol

1784

It is no exaggeration to say that on Sundays in Washington during the administrations of Thomas Jefferson (1801-1809) and of James Madison (1809-1817) the state became the church. Within a year of his inauguration, Jefferson began attending church services in the chamber of the House of Representatives. Madison followed Jefferson's example, although unlike Jefferson, who rode on horseback to church in the Capitol, Madison came in a coach and four. Worship services in the House—a practice that continued until after the Civil War—were acceptable to Jefferson because they were nondiscriminatory and voluntary. Preachers of every Protestant denomination appeared. (Catholic priests began officiating in 1826.) As early as January 1806 a female evangelist, Dorothy Ripley, delivered a camp meeting-style exhortation in the House to Jefferson, Vice President Aaron Burr, and a "crowded audience."[32]

United States Capitol

1785

Not long after the completion of both wings, the Capitol was partially burned by the British on August 24, 1814, during the War of 1812. George Bomford and Joseph Gardner Swift, both military engineers, were called upon to help rebuild the Capitol. Reconstruction began in 1815 and included redesigned chambers for both Senate and House wings (now sides), which were completed by 1819. During the reconstruction, Congress met in the Old Brick Capitol, a temporary structure financed by local investors. Construction continued through to 1826, with the addition of the center section with front steps and columned portico and an interior Rotunda, rising above the first low dome of the Capitol. Latrobe is principally connected with the original construction and many innovative interior features; his successor, Bulfinch, also played a major role, such as the design of the first low dome covered in copper.

United States Capitol

1786

By 1850, it became clear that the Capitol could not accommodate the growing number of legislators arriving from newly admitted states. A new design competition was held, and President Millard Fillmore appointed Philadelphia architect Thomas U. Walter to carry out the expansion. Two new wings were added – a new chamber for the House of Representatives on the south side, and a new chamber for the Senate on the north.[33]

United States Capitol

1787

When the Capitol was expanded in the 1850s, some of the construction labor was carried out by slaves "who cut the logs, laid the stones and baked the bricks".[34] The original plan was to use workers brought in from Europe; however, there was a poor response to recruitment efforts, and African Americans, some free and some enslaved, composed the majority of the work force.[35]

United States Capitol

1788

The 1850 expansion more than doubled the length of the Capitol, dwarfing the original, timber-framed, copper-sheeted, low dome of 1818, designed by Charles Bulfinch and no longer in proportion with the increased size of the building. In 1855, the decision was made to tear it down and replace it with the "wedding-cake style" cast-iron dome that stands today. Also designed by Thomas U. Walter, the new dome would stand three times the height of the original dome and 100 feet (30 m) in diameter, yet had to be supported on the existing masonry piers. Like Mansart's dome at "Les Invalides" (which he had visited in 1838), Walter's dome is double, with a large oculus in the inner dome, through which is seen "The Apotheosis of Washington" painted on a shell suspended from the supporting ribs, which also support the visible exterior structure and the tholos that supports The "Statue of Freedom", a colossal statue that was raised to the top of the dome in 1863. This statue was cast by a slave named Philip Reid. The weight of the cast iron for the dome has been published as 8,909,200 pounds (4,041,100 kg).[36]

United States Capitol

1789

When the Capitol's new dome was finally completed, its massive visual weight, in turn, overpowered the proportions of the columns of the East Portico, built in 1828. The East Front of the Capitol building was rebuilt in 1904, following a design of the architects Carrère and Hastings, who also designed the Russell Senate and Cannon House office buildings.

United States Capitol

1790

The next major expansion to the Capitol started in 1958, with a 33.5 feet (10.2 m) extension of the East Portico.[citation needed] During this project, in 1960 the dome underwent a restoration.[37] A marble duplicate of the sandstone East Front was built 33.5 feet (10.2 m) from the old Front. (In 1962, a connecting extension incorporated what had been an outside wall as an inside wall.) In the process, the Corinthian columns were removed. It was not until 1984 that landscape designer Russell Page created a suitable setting for them in a large meadow at the U.S. National Arboretum in northeast Washington as the National Capitol Columns, where they are combined with a reflecting pool in an ensemble that reminds some visitors of the ruins of Persepolis, in Persia. Besides the columns, hundreds of blocks of the original stone were removed and are stored behind a National Park Service maintenance yard in Rock Creek Park.[38]

United States Capitol

1791

On December 19, 1960, the Capitol was declared a National Historic Landmark by the National Park Service.[39] The building was ranked #6 in a 2007 survey conducted for the American Institute of Architects' "America's Favorite Architecture" list.[40] The Capitol draws heavily from other notable buildings, especially churches and landmarks in Europe, including the dome of St. Peter's Basilica in the Vatican and St. Paul's Cathedral in London.[41] On the roofs of the Senate and House Chambers are flagpoles that fly the U.S. flag when either is in session. On September 18, 1993, to commemorate the Capitol's bicentennial, the Masonic ritual cornerstone laying with George Washington was reenacted. U.S. Senator Strom Thurmond was one of the Freemason politicians who took part in the ceremony.

United States Capitol

1792

On June 20, 2000, ground was broken for the Capitol Visitor Center, which opened on December 2, 2008.[42] From 2001 through 2008, the East Front of the Capitol (site of most presidential inaugurations until Ronald Reagan began a new tradition in 1981) was the site of construction for this massive underground complex, designed to facilitate a more orderly entrance for visitors to the Capitol. Prior to the center being built, visitors to the Capitol had to line up in the basement of the Cannon House Office Building or the Russell Senate Office Building. The new underground facility provides a grand entrance hall, a visitors theater, room for exhibits, and dining and restroom facilities, in addition to space for building necessities such as an underground service tunnel.

United States Capitol

1793

A large-scale Capitol dome restoration project, the first extensive such work since 1959–1960, began in 2014, with completion scheduled before the 2017 presidential inauguration.[43] As of 2012, $20 million in work around the skirt of the dome had been completed, but other deterioration, including at least 1,300 cracks in the brittle iron that have led to rusting and seepage inside, needed to be addressed. Before the August 2012 recess, the Senate Appropriations Committee voted to spend $61 million to repair the exterior of the dome. The House wanted to spend less on government operations,[37] but in late 2013, it was announced that renovations would take place over two years, starting in spring 2014.[44] Extensive scaffolding was erected in 2014, enclosing and obscuring the dome.[43] All exterior scaffolding was removed by mid-September 2016.[45]

United States Capitol

1794

The Capitol building is marked by its central dome above a rotunda in the central section of the structure (which also includes, the older original smaller center flanked by the two original (designed 1793, occupied 1800) smaller two wings (inner north) and inner south) containing the two original smaller meeting chambers for the Senate and the House of Representatives (between 1800 and late 1850s) and then flanked by two further extended (newer) wings, one also for each chamber of the larger, more populous Congress: the new north wing is the Senate chamber and the new south wing is the House of Representatives chamber. Above these newer chambers are galleries where visitors can watch the Senate and House of Representatives. It is an example of the neoclassical architecture style.

United States Capitol

1795

Underground tunnels and internal subways connect the Capitol building with the Congressional office buildings in the Capitol Complex. All rooms in the Capitol are designated as either S (for Senate) or H (for House), depending on whether they are in the Senate or House wing of the Capitol.

United States Capitol

1796

The Capitol has a long history in art of the United States, beginning in 1856 with Italian/Greek American artist Constantino Brumidi and his murals in the hallways of the first floor of the Senate side of the Capitol. The murals, known as the Brumidi Corridors,[46] reflect great moments and people in United States history. Among the original works are those depicting Benjamin Franklin, John Fitch, Robert Fulton, and events such as the Cession of Louisiana. Also decorating the walls are animals, insects and natural flora indigenous to the United States. Brumidi's design left many spaces open so that future events in United States history could be added. Among those added are the Spirit of St. Louis, the Moon landing, and the Space Shuttle Challenger shuttle crew.

United States Capitol

1797

Brumidi also worked within the Rotunda. He is responsible for the painting of "The Apotheosis of Washington" beneath the top of the dome, and also the famous "Frieze of American History".[47] "The Apotheosis of Washington" was completed in 11 months and painted by Brumidi while suspended nearly 180 feet (55 m) in the air. It is said to be the first attempt by the United States to deify a founding father. Washington is depicted surrounded by 13 maidens in an inner ring with many Greek and Roman gods and goddesses below him in a second ring. The frieze is located around the inside of the base of the dome and is a chronological, pictorial history of the United States from the landing of Christopher Columbus to the Wright Brothers's flight in Kitty Hawk, North Carolina. The frieze was started in 1878 and was not completed until 1953. The frieze was therefore painted by four different artists: Brumidi, Filippo Costaggini, Charles Ayer Whipple, and Allyn Cox. The final scenes depicted in the fresco had not yet occurred when Brumidi began his "Frieze of the United States History".

United States Capitol

1798

Within the Rotunda there are eight large paintings about the development of the United States as a nation. On the east side are four paintings depicting major events in the discovery of America. On the west are four paintings depicting the founding of the United States. The east side paintings include The Baptism of Pocahontas by John Gadsby Chapman, The Embarkation of the Pilgrims by Robert Walter Weir, The Discovery of the Mississippi by William Henry Powell, and The Landing of Columbus by John Vanderlyn. The paintings on the west side are by John Trumbull: Declaration of Independence, Surrender of General Burgoyne, Surrender of Lord Cornwallis, and General George Washington Resigning His Commission. Trumbull was a contemporary of the United States' founding fathers and a participant in the American Revolutionary War; he painted a self-portrait into Surrender of Lord Cornwallis.

United States Capitol

1799

First Reading of the Emancipation Proclamation of President Lincoln hangs over the west staircase in the Senate wing.[48]

United States Capitol