OF ARTS AND SCIENCES. 175 



IX. 



ON THE LONGITUDE OF WALTHAM, MASS. 

 By Leonard Waldo, 



Assistant at the Observatory of Harvard College. 

 Presented Nov. 14, 1877. 



At the request of the Mechanical Superintendent of the American 

 "Watch Company's factory in Waltham, Mass., the longitude of their 

 private observatory has been determined as nearly as may be from one 

 night's exchange of signals ; and, as that observatory is near a Coast- 

 Survey station, the result has sufficient value to be placed on record 

 for any investigation relative to the problem of station error. 



The manner of determining the longitude was as follows : In 

 order to eliminate, as far as possible, the errors in the resulting longi- 

 tude arising from the lack of a simultaneous action among all the 

 armatures of the electro-magnets used in transmitting and recording 

 the clock-beats at the two stations, it was arranged that both observers 

 should use the same clock, and should, as far as possible, have the 

 same manner of connections at both observatories. The mean-time 

 Bond clock, used for time signals at 97 Water Street, was therefore 

 employed. This clock, working through the private wires operated by 

 the time-service of the observatory, and by the American Watch 

 Company, recorded its beats simultaneously at Waltham and at Cam- 

 bridge. At both these stations, local circuits included a chronograph, 

 a relay worked by the Boston clock, and the observing key of the 

 observer. 



The observations were made at Cambridge with the broken-tele- 

 scope transit, by M. Herbst of Poulkova. This is the instrument 

 ordinarily used for time observations, and may be found figured and 

 described in vol. viii. of the " Annals of Harvard College Observa- 

 tory." It has a clear aperture of 2.75 inches, and a focal length 

 of 32.68 inches, nearly. The pivots are of steel, 1.195 inches in 

 diameter, and sensibly equal. They rest upon V-shaped gun-metal 

 bearings, which are 0'".16 in breadth, and whose centres are distant 



