The masonry pier that supports the Ladd Observatory’s main telescope contains two clock vaults. These are very small rooms (4 by 4 feet square inside) that contain precision pendulum timepieces called regulators. The purpose of a clock vault is to provide a vibration-free and temperature-stable environment for exact timekeeping. The main clock vault is located in the entrance foyer on the first floor of the Observatory. The basement level vault has not been used in many years. Professor Winslow Upton calibrated the regulators using observations of stars starting in the 1890s.
The double doors to the vault seal out drafts and have windows through which the regulators can be observed without disturbing the environment inside. The brick walls are two feet thick which provides insulation to prevent fluctuating temperatures which could cause inaccuracy. There are telegraph wires to send time signals from the regulators to other locations around Rhode Island. Starting September 12, 1893 and continuing until as late as 1973 the Observatory also transmitted time signals to City of Providence fire stations. Every day at noon and 8:30 p.m. signals sounded on the fire-alarm bells allowing residents and businesses to set their clocks to the correct time. Public time signaling was a common practice during this era.
“This is truly scientific magic. Just think of it! You want to know the true time to the fraction of a second, and all you have to do in order to get it is to open your electric ear to these sounds, which seem to drop out of the sky, as if Old Time himself were speaking to you!”
During 1913 the Washington Naval Observatory and the Observatoire de Paris attempted to exchange wireless time signals. The experiment was used to calculate the difference in longitude between the two locations more accurately than was possible with other techniques. They were also trying to measure the velocity of radio waves through space. The goal was to improve communication with ships at sea which used the time signals to calibrate the chronometers used for celestial navigation. For most of the year atmospheric conditions prevented the reception of the signals sent across the ocean. The conditions improved in November and the two observatories were then in regular contact by radio. Prof. Winslow Upton of Ladd Observatory was listening in on the transmissions.
Prof. Winslow Upton tapped a telegraph key as he watched the planet Mercury transit the Sun. The signal was sent to a chart recorder where an electromagnet moved a pen on a slowing turning drum of paper to record the observation. The instrument is called a chronograph. This one was made by the Warner and Swasey Company of Cleveland in 1890. Primarily it was used for calibrating the astronomical regulators (precision pendulum clocks) to set the time accurately. It was also used for timing events such as lunar occultations of stars.