14 E. Loomis— Contributions to Meteorology. 
mean temperature of the air-column remains unchanged, the 
observed change in the reduction to the lower station reatllie 
from a change of pressure at the upper eee is only one 
of that computed from the formula. Thus we see that the re- 
duction of barometric observations to sea-level 7a se different 
aws at different localities. The following table shows a sum- 
mary of these results for these five mountain stations : 
Change of reduction depending upon 
ation: Thermometer arometer. 
Mt. Washington, v13 0°142 
Pike’s Peak, 675 + 195 
Summit, Cal., 590 — °866 
Grand St. Bernard, 912 + 989 
Colle di Valdobbia, “695 + +500 
Mean, “769 + °192 
Coluinn Ist shows the names of the mountain stations; col- 
umn 2d shows the average values of the observed change in the 
reduction to the lower station resulting from a change in the 
ail eater of the air-column, and compared with the change 
mputed from the formula; column 3d shows the average 
wits of the observed change i in the reduction resulting from a 
change of pressure at the upper station, and compared with the 
computed cha 
A comparison : these results shows that the temperature 
coéfficient emplo y Deleros and Guyot is too large; an 
the observed value of the reduction to sea-level would in most 
cases be somewhat better represented by assuming a larger 
value for the coéfficient 18336 meters or 60158°6 English feet 
adopted by Laplace from the observati ions of Ramond made 
aie reduction to sea-level with tolerable accuracy. The aver- 
age of a long series of observations represents approximately 
such a condition of equilibrium; but in the daily Sey Mee 
this equilibrium is very much disturbed. The mean between 
the temperatures at the upper and lower gious | ates not 
represent the average temperature of the intermediate column 
of air; and when the atmosphere is in rapid motion the down- 
ward pressure is modified by the earth’s rotation in a manner 
not represented by the Laplace formula. There is no doubt 
that the formule of reduction now employed may be consider- 
- improved ; but it does not seem possible that any single 
