30 



topographer; Carl Easkopfif, assistant topographer; C. E. Fellerer, assistant; Wm. M. Ord, 

 assistant, with the necessary number of guides, packers, laborers, &c., and an escort of two non- 

 commissioned officers and twenty-three enlisted men of Company H, Eighth United States Cavalry. 



LONGITUDE BY TELEGEAPH. 



While sextants and chronometers are the most accurate instruments that can be readily trans- 

 ported by parties moving rapidly in the field, and latitude can be determined sufficiently accurate 

 for ordinary practical purposes by their use, the question of longitude is exceedingly uncertain, 

 since so very strange are some of the inaccuracies of rate in the chi'onometers that, no matter how 

 many are used, the results must be accepted with caution. Being well aware of these facts, 

 arrangements were made, while preparing for the season's work, to take advantage of the telegraph, 

 to find out at any moment the local errors of the chronometers upon Sau Francisco time. It was 

 deemed possible to accomplish this at four points, viz, Elko, Peko, Euby, and Hamilton. With 

 the two latter places the lines of the Western Union Telegraph Company connect, and through 

 the kindness of the managers at San Francisco, Messrs. Mumford, Ladd, and Yountz, i)ermission 

 was granted for the use of their lines, and a letter of instructions to their agents in Euby Valley 

 and Hamilton was furnished ; besides, they very kindly arranged,through Mr. Yaudenberg, at Sac- 

 ramento, the superintendent of the lines of the Central Pacific Eailroad, to connect, so that a com- 

 plete circuit should exist between San Francisco and points on the Central Pacific Eailroad, near 

 Camp Hiilleck. Prof. George Davidson, United States Coast Survey, whose kindness in this 

 matter is worthy of many thanks, offered to take charge of the signals at Sau Francisco, but he 

 was obliged to start on his trip to the North to observe during the solar eclipse. Prior to our 

 reaching Camp Halleck, Maj. H. M. Eobert, Corps of Engineers, having been spoken to upon this 

 matter, his co operation was at once enlisted, and, out of the five times that telegraphing was done, 

 he was at the key during four of them; the other, being the one at Elko, was superintended 

 through the kindness of Capt. H. J. Eogers, United States Coast Survey. 



The scheme for attaining accuracy in the recording of the signals was furnished by Professor 

 Davidson, of the Coast Survey, a copy of which is herewith given. 



PROGKAMME TOR DETERMINATION OF DIFFERENCE OF LONGITUDE BY TELEGRAPH BETWEEN SAN 

 FRANCISCO, CAL., AND STATIONS IN NEVADA— PROPOSED BY PROF. GEORGE DAVIDSON, UNITED 

 STATES COAST SURVEY. 



Lieutenant Wheeler to telegraph to San Francisco immediately upon Lis arrival at any station, 

 and say when he will be ready to receive signals. 



To receive them he will have his chronometer ready at the telegraph-office. When Professor 

 Davidson or Major Eobert is ready, he will send message to Elko, or the station, to that effect, 

 and, after preliminaries, for a few minutes will carry out the following programme: Professor Da- 

 vidson or INfajor Eobert : Battle, rattle, rattle ; interval of fifteen seconds ; then transmit one signal 

 of which Lieutenant Wheeler must note the time by his chronometer; a second signal fifteen 

 .seconds later, and so on, one signal every fifteen seconds for three minutes, then three rattles to 

 close. 



Then Lieutenant Wheeler will send to Professor Davidson or Jlajor Eobert a similar set of 

 sigiuils at given times, of fifteen seconds apart, for three minutes by his chronometer. Professor 

 Davidson or Major Eobert will then send San Francisco time of his first and last sigual, also the 

 error of his chronometer on San Francisco time. 



Lieutenant Wheeler will send his chronometer time of first and last signals and the error of 

 his chronometer, if obtained ; if not known, then he will transmit it by rail as soon as ascertained. 



When Lieutenant Wheeler returns from his trip this programme can be repeated previous to 

 his return to-San Francisco. 



The above scheme has been carried out, and the following tables show the details ot the 

 results : 



