E. Loomis—Reduction of Barometric Observations. 18 
four tenths of an-inch: and at the secondary minimum of Dec. - 
24.3, 1872, the barometer at sea-level had already risen above 
the preceding minimum a half inch more than the Mt. Wash- 
ington barometer had risen. A similar case occurred Dec. 30.2, 
1874. The discrepancies sbown in table V are due partly to the 
causes here stated, and partly to the violence of the winds on 
Mt. Washington, for according to theory, the velocity of the 
wind is the most important factor which determines the depres- 
sion of the barometer in a great storm. 
The.excess of the barometric pressure at sea-level above the 
Mt. Washington observations reduced to sea-level as shown by 
table III in the case of barometric minima, is ascribed to the 
same causes. 
IIT are explained in a somewhat similar manner. From the 
even more. 
If we attempt to represent the reduction of the Mt. Washing- 
ton observations to sea-level by the Laplace formula with 
modified coefficients, we find that the high pressures require a 
larger value of the pressure coefficient than the low pressures. | 
Also that the low temperatures require a larger value of the 
temperature coefficient than the high temperatures. It is not 
possible therefore to find values for these coefficients which 
shall represent the observed reduction for all pressures — 
temperatures. I have sought to obtain values which shall best 
represent all the observations, and in doing this I have given 
the observations made near the time of barometric maxima, 
twice the weight of those made near the time of barometric — 
minima, for the reason that in the former case the winds are 
more feeble, and the atmosphere probably approaches nearer to 
the condition of statical equilibrium. With this assumption I 
have found that the value of the pressure coefficient which best 
represents the Mt. Washington observations is 60372, and that 
sure coefficient employed by Laplace (60158°6) is too small. _ 
I next undertoo il i serv 
on Pike’s Peak and Denver. Table VI shows the princi 
‘barometric minima on Pike’s Peak during a period of three 
a 
