10 £E. Loomis—Observations of the U. S. Signal Service. = 
It will be seen that in one instance the minimum at Mt 2 
Washington occurred earlier than it did at Burlington or Port — 
land; in eight cases the minima occurred simultaneously; in 
seventy cases the minimum on Mt. Washington occurred later _ 
than the half sum of the dates at Burlington and Portland, the 
average difference being 0°88, or seven hours. The height of 
Mt. Washington above Burlington and Portland is 6,148 feet, 
showing an average retardation of one hour for an elevation of 
870 feet. 
I next compared the observations made at the summit of Mt. — 
Mitchell in North Carolina (elevation 6,691 feet) with those 
made at the base of the mountain (elevation 2,560 feet) from 
August 6th to September 5th, 1873, published in the Report of 
the United States Chief Signal Officer for 1878, but the fluctu- — 
ations of the barometer were too small to yield satisfactory — 
results. The following are the most noticeable coincidences of 
minimum pressure : 
Base. Summit. | Difference. 
1873. Aug. 13} 3 P.M. 4p.M. |+1] hour. 
15 
A.M 5a.M. |+3 hours 
25| 5 PM. TPM. }+2 
27] 2 xe. 4aM. | +2 
Sept. 4) 3PM. TPM, |+4 
5} 3PM 6 P.M. +3 
These results indicate an average retardation of one hour for an 
elevation of 1,600 feet, but the fluctuations are so small that 
no great importance can be attached to them except as they 
are taken in connection with other observations. 
I next compared the observations made on Pike’s Peak (ele- 
orado Springs and Pike’s Peak, and the last column shows the 
difference between the dates of the critical points at the two 
stations. 
