The earliest clocks produced were intended for public (usually religious) buildings. These huge, costly clocks, usually placed in towers or turrets for maximum audibility and/or visibility, spread through Europe throughout the 14th, 15th, and 16th centuries, fostering in people a greater sense of temporal awareness. It is not surprising that early colonists accustomed to such clocks were quick to import them from England and erect them in their new land. The first clock in the colonies was mounted in Boston in 1668, and others soon followed. These impressive public symbols and instruments of civic order were not limited to big cities, but also appeared in small towns. A public clock was often located in the center of town, usually in a large, significant building like a church or meeting hall. Next to the sun, this clock was the closest thing a town had to temporal authority.
By the mid 19th century, tower clocks were being mass-produced in the US and installed in thousands of towns throughout the country, in courthouses, churches, city halls, schools, and other private and public buildings. The two biggest manufacturers of tower clocks were the Seth Thomas and E. Howard clock companies. During the 20th century, many original mechanical movements have been discarded or replaced with electrically driven mechanisms.
From the 1890s through the 1920s another form of American public clock became popular—the street clock. far less expensive than tower clocks, these clocks were still very visible and impressive. Cased—sometimes rather decoratively—in cast iron, these clocks usually had two or four dials, and either stood on a sidewalk or were mounted on the corner of a building. Dials were commonly two to three feet in diameter, and examples designed to stand on the sidewalk might rest on a post eight feet high or taller. Businesses often used these clocks to advertise their establishments while providing a useful public service.
One of the world's most famous and beloved clocks is the great tower clock at the Palace of Westminster in London, England. Although the entire clock, the tower, and even the surrounding precincts are variously called Big Ben, the name technically refers only to the huge 13.5-ton bell that sounds the hours. The origin of the bell's name is unclear. Some say its eponym was Sir Benjamin Hall, First Commissioner of Works, 1855-58; others claim that either one of two well-known prize fighters, Benjamin Brian or Benjamin Gaunt, could have served as its inspiration. And yet others assert that "Big Ben" was simply 19th-century slang for anything that was the biggest of its kind.
The clock's huge iron mechanism (over fifteen feet long and almost five feet wide) was built by Fredrick Dent from the design of Edmund Denison. Although completed in 1854, it was not installed until 1859, when construction of the tower permitted. It contains three interlinked trains of gears and drums: the time train, the striking train, and the chiming train. Although the time train is the smallest, it is the heart of the clock, providing the energy to drive the hands, sustain the thirteen-and-a-half-foot-long pendulum which regulates the clock's rate, and control the operation of the two other trains which drive the bells.
For the sake of precision, Big Ben and the four quarter bells are all struck with hammers rather than swung—the hour bell 156 times a day, and the quarter bells a collective total of 960 times a day. Only a few weeks after its inaugural striking, the great hour bell developed a crack which remains to this day (Big Ben itself was actually cast after the clock's first bell cracked prior to installation). Big Ben's E Natural note is as distinctive as the music of the Westminster chimes, which is based on the aria from Handel's Messiah.
Big Ben owes a lot of its visual impact to its four dials, each of which measures 23 feet in diameter and contains 312 irregular panes of opalescent glass set in a cast iron tracery. The numerals are two feet high and written in unusual Gothic calligraphy. The dial faces were illuminated with gas lamps until 1906, at which time electric lighting was used. In 1957, vastly brighter cold cathode lights were installed, which are still in use today. The dials cost more than the clock mechanism and the bells combined.
Here are some of the museum's featured tower clocks: