J. Rodgers— Observations on the Transit of Mercury. 455 
Another subject which has received much attention is the 
utilization of the pasturage lands; and still another, the best 
methods of surveying the mineral lands for the purpose of 
description and identification, that the owners of mines may be 
relieved of the great burden of litigation to which they are 
subjected by reason of the inaccurate and expensive methods 
now in vogue. 
Arr. LXVL— Observations on the Transit of Mercury. Letter 
to the Editors from JoHn Rop@ers, Rear Admiral U.5.N., 
Superintendent of the United States Naval Observatory, 
dated May 11, 1878. 
Ir may interest your readers to learn that the transit of Mer- 
cury, occurring on May 5-6, was very successfully observed 
at the Naval Observatory, and throughout the country gen- 
erally. Satisfactory observations of all the contacts were made 
here, and good observations of the contacts have been reporte 
from the observers of the United States Coast Survey in 
Washington, and in different parts of the country. Reports of 
observations of the contacts have been received from 
observatories at Cambridge and at Ann Arbor, Professors 
Pickering and Watson, kindly undertook the work of making 
i ies: and a set of the instru- 
photographs was the same as that followed in the case of the 
transit of Venus. The dry-plate process Was, however, 
adopted in the present case, in place of the wet-plate process 
used in the transit of Venus. The great advantage of the 
dry-plate process, if it can be used successfully, 1s evident. 
The plates were all prepared here by Mr Joseph A. Rogers ; 
and seventy-two plates were sent to each of the observatories, 
where they were exposed and then returned here for develop- 
ment. The same number of plates were exposed here by Mr. 
