442 G.W. Dean—Longitude Det-rmination across the Continent. 
At Omaha, the clock and instrumental corrections were 
determined by Assistant Edward Goodfellow and Mr. E. P. 
ustin, who used a forty-six-inch transit with an aperture of 
two and three-fourths inches. All the observations were re- 
corded by an astronomical clock in connection with a chrono- 
graph register. At Salt Lake City, the clock and instrumental 
corrections were determined by myself, assisted by Mr. F. HL 
Agnew, Sub-Assistant in the Coast’ Survey. 
The instruments used were similar to those provided for the 
stations at Omaha and San Francisco. 
Assistant George Davidson had charge of the longitude opera- 
tions at San Francisco, and codperated with Professor Winlock 
and myself in making the telegraphic longitude determinations 
across the Continent. : 
Cold dry weather being most favorable for exchanging tele- 
graph signals between Uistant stations, arrangements were made 
for these experiments during the winter of 1868-69. 
Whenever the weather permitted, the clock and instrumental 
corrections at each station were carefully determined, imme- 
diately before and after the exchange of clock signals between 
correction in no case exceeded 0°05 seconds. Mayer's formule, 
by application of the method of least squares, have been used 
in these reductions, which have been made in the most satis- 
ts. 
In closing this paper, I will state, that on the nights of Feb- 
ruary 28th and March 7th, 1869, the Western Union Telegraph 
science, placed two of their telegraph lines, between Cambri 
and San Franci 
purpose of measuring the “transmission time ” of ‘signals sent 
rom Cambridge to San Francisco and returned, and “ vice versd. 
The entire length of the several circuits, which were com- 
e ul d closely with 
the “double transmission time” deduced from the longitude 
: determinations between Cambridge and San Francisco, and ast 
ae with the. results of the experiments made for “ transmissiou 
time” with a single wire between those points, by Professor 
mock and Assistant Davidson. 
Company, with their usual liberality for the advancement of 
