1 882. S7 Trans. N. V. Ac. Sd. 



5. The Observatory at Mount Lookout, near Cincinnati, supplies the 

 city with time-signals, and several railroads get their time trom 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 building, and clock signals are sent to 

 many subscribers in the city. The central clock here is regulated by 

 time-signals received from the Navil Observatory at Washington, 

 Irom Professor Langley's observatory at Allegheny, Pa., and Irom 

 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 statu'.e inakmg the use of New York time 

 compulsory upon all transportatiDn companies within her limits."* 



8. The Dearborn Observatory, of Chicago, is the centre of that city's 

 time-system, and supplies several railroads with time-5ignals. 



9. Radiating from the Observatory of Washington University, St. 

 Louis there is a city time-service cf considerable extent.'' 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. 



10. The Morrison 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 neighboring clocks. 



Every year the demand for accurate time beco nes stronger and 

 more extended. The supply is fully equal to th-^ demand ft 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 lourteen mdes 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 



