E.. Loomis— Contributions to Meteorology. 5 
as that given by the formula of Laplace. The influence of 
mperature on the reduction to sea-level, as deduced from the 
shuerrasiouk differs but little from that given by the formula 
of Laplace. At the highest temperatures, the observed redue- 
tion accords saith that computed by the formula when the pres- 
sure at sea-level is 29°8 inches; and at the lowest temperatures 
the agreement occurs when the pressure at sea-level is 30°7 
inches. Thus we see that the true reduction of barometric ob- 
servations to sea- ee for Mt. Washington depends mainly 
upon temperat 
he shasta. ows of the reduction to sea-level given in 
the table on page 4 are in all cases the means of a considera- 
ble number of observations. In some cases the observed val- 
ues differ very much from the means here given. In order to 
learn the magnitude of these differences and to study the cir- 
cumstances under which they occur, I proceeded as follows: 
I selected all those cases (for the thirty- six months of the tri- 
daily observations) in which the reduction computed by Dun- 
woody’s Tables differed by 0°25 inch from the observed reduc- 
tion. ‘The number of these cases was ninety-six. As this table 
seemed too large for publication, I selected those cases in which 
the difference amounted to at least 0°3 inch and for these cases 
the reduction to sea-level was a computed by the for- 
mula of Laplace. The results are given in the following table, in 
which column 1st shows the number of the storm; column 2d 
shows the date of the observation; column 3d shows the shee 
ed height of the barometer on Mt. Washington, not reduced to sea- 
level. This observed height was obtained by subtracting 6°31 
inches from the published ‘heights for all dates preceding March, 
1874, and subtracting 6:36 inches for subsequent dates. Column 
4th shows the mean temperature of the air column from the 
Cae) 
summit to the base of the mountain column d5th 
shows the observed reduction to sea-level (“t-—w); column — 
6th shows the reduction to sea-level computed by Laplace’s for- 
mula, for a height 6,285 feet, with a barometer and temperature 
as given in columns 3and 4; column 7th shows the reduction ac- 
cording to the table on p. 4, in the lines marked O; column 8th 
shows the difference between the numbers in columns 5 and 6: 
column 9th shows the difference between the numbers in columns 
5and 7; column 10th shows (in hours) how much the minimum 
pressure on Mt. Washington occurred later than the half sum of 
the dates of minimum at Burlington and Portland; column 11th 
shows the direction and force of the wind on Mt. Washington. 
The number of cases in this table is 40, of which 8 occurred 
in November; 11 in December; 12 in January ; 2 in Febru- 
