ee a AE ae LT oe er on Sieet LO rate 
ae grea 2 Mesh Peels 
yg gay Bhd) Peel ear AS Ree he RE AY 
H. A. Hazen—Reduction of Air-pressure to Sea-level. 455 
The computed result is the smallest for a low temperature and 
high pressure, and largest for a high temperature and low pres- 
2 
sure. an these variations be accounted for? 
All who have discussed this subject are agreed that some 
modification of the formula is necessary. R. S. Williamson has 
ters at different altitudes, but not separated by any great dis- 
tance horizontally, we have at once the weights of a column 
would seem at first sight as if trustworthy results, or, at least, 
a very close approximation to the truth might be obtained. La- 
place was the first to propose a complete formula.” On page 13 
“Laplace's original formula comprised four terms, 
which may be designated as the pressure term, including, as is 
After an extended discussion entirely upon a theoretical basis, 
rof. Whitney concludes, “ T ; 
considered essentially unalterable.” He considers that all the 
et us examine these points: if the only motions of the 
atmosphere were in a vertical direction and due essentially to 
the temperature, the solution of the problem would appear not 
difficult. 
At first sight it seems as though the temperature term would 
be the easiest determined and tie one least liable to change, for 
the reason that the temperature is almost entirely affected by 
only one great invariable cause. Thus we find the same mean 
temperature in April and October of each year, the lowest in 
