• In the late 1500s, Galileo used his own pulse to count time for experiments and discovered that the pendulum was a more accurate method of marking off small intervals of time. But it was not until 1656 that the Dutch astronomer Christiaan Huygens built the first clock using pendulums to keep seconds and, after enclosing the clockworks in wood, hung it on the wall. Until the late mid- to late 1600s, time was recorded in broad representations by the hour.
  
  

Cuckoo Clocks

• The history of the cuckoo clocks is a matter of pride when it comes to the clock makers in the Black Forest region of Germany. History credits Franz Anton Ketterer around 1738 with building the first cuckoo clock, a rough manifestation of the elegant, hand-carved pieces that are offered up by German clockmakers today. The Duke of Baden built a clockmaking school in Furtwangen in 1850, and the region is just as distinguished today for its cuckoo clocks ranging in sizes from around 6 inches to gargantuan devices standing taller than an average-sized person.
  
  There are several different styles of cuckoo clocks available, including the Hunter style with its animals (alive or dead), guns, powder horns and pouches and the Bahnhäusle style with grapevines. The clock can have just a simple door above the clock face through which a cuckoo announces the hours, but each clock can also be built with elaborate movements and characters to go along with music.
  
  

Pendulum Clocks

• Pendulum clocks can be quite elegantly made, with wood cases, accents and elaborate pendulums behind etched-glass doors. Today's pendulum clocks offer such luxuries as night-time chime shut-offs with or without the hourly sounding. The shapes of the casings also come in a wide range of styles, such as octagonal faces, plain or carved tops, and with and without closures for the pendulums. Pendulum clocks also come in a broad range of sizes, depending on needs or desires.
  
  

Standard Wall Clocks

• A simple round wall clock with a white face, black numbers, and standard hour and minute hands adorns many schools and doctor's offices around the United States. The variety of styles available in standard wall clocks is just as extensive as in pendulum and cuckoo clocks. Today's clocks can incorporate other functions such as hygrometers (which measure relative humidity) and thermometers. Rather than just being offered in the traditional white clock face in a round case, the styles can be more colorful and adorned with designs. Digital wall clocks are also available that can include date features and vary between 12-hour and 24-hour time formats.
  
  

Radio-Controlled Clocks

• Some wall clocks have the luxury feature of being radio-controlled. As long as a power source is available, the clock receives a low frequency signal from the National Institute of Standards and Technology in the United States and keeps the time, never having to be adjusted even for daylight saving time. Radio-controlled clocks are available as standard clocks with the round face with hour and minute hands, or they can be digital.