1882, 87 Trans. N. Y. Ac. Sct. 
5. The Observatory at Mount Lookout, near Cincinnati, supplies the 
city with time-signals, and several railroads get their time from the 
Same observatory.’ . 
6. The New York City system is under the control of the Western 
Union Telegraph Company. A noon-time ball is dropped from a pole 
on the roof of the company’s build:ng, and clock signals are sent to 
‘many subscribers in the city. The central clock here is regulated by 
time-signals received from the Naval Observatery at Washington, 
from Professor Langley’s observatory at Allegheny, Pa., and trom 
Harvard Observatory. 
7. The Winchester Observatory (Yale College) system distributes 
time to the railroads and to several cities in the State of Connecticut. 
The State ‘“‘has enacted a statute making the use of New York time 
compulsory upon all transportation companies within her limits.’’8 
8. The Dearborn Observatory, of Chicago, is the centre of that city’s 
time-system, and supplies several railroads with time-signals. 
g. Radiating from the Observatory of Washington University, St. 
Louis, there is a city time-service of considerable extent.2 Arrange- 
ments have been made to send time-signals over the railroad lines 
centering at St. Louis, South as far as Texas, and West probably as 
far as Denver. 
Io. The Morrisen Observatory, at Glasgow, Missouri, us'ng Western 
Union wires, row drops noon-time balls, at St. Louis and at Kansas 
‘City, and sends time-signals along several railroads. 
These are the most prominent time-centres in the United States. But 
there are many other centres of less importance. From almost every 
public and private observatory time is sent, in one way or another, for 
the regulation of ne?ghboring clocks. 
Every year the demand for aceurate time becones stronger and 
more extended. The supply is fully equal to the demand It is pos- 
sible for any business concern or private indiv dual to obtain accurate 
time from some observatory near by at very small expense and trouble. 
The instant of mean or clock noon, at any place, is the time when 
the mean sun is on the meridian of the place. It is noon then for all 
places on that meridian. In four and a half seconds (for lat. 40°40) 
it is noon for places on the meridian about one mile west of the 
first meridian. Places about tourteen miles west of the first meridian 
will have local noon one minute later, and so on. 
No two places can have, astronomically speaking, the same local 
times unless they are on the same meridian. 
In large cities, and over lines of railroads, it has long been the custom 
to disregard the changes in the local times as we pass to the east and 
to the west; and the time, say, of the City Hall is used as the standard 
