2 EE. Loomis—Reduction of Barometric Observations. 
ton from Portland is almost exactly two-thirds of its distance 
from Burlington, and I have assumed that the pressure at sea- 
level under Mt. Washington is given by the formula #(2B+38P). 
The temperature at sea-level given in column fourth is deduced 
from the observations at Burlington and Portland by the same 
formula. Column fifth shows the pressure observed on Mt. 
Washington, column sixth the temperature on Mt. Washington 
and column seventh gives the half sum of the temperatures in 
columns four and six. 
- The numbers in this table were arranged in the order of the 
mean temperatures given in column seventh, and were divided 
into four equal groups and the average of the numbers in the 
several columns for each group was computed. The results 
are given in the first five lines of table III, under the heading 
barometric minima; and these results may ‘be regarded as nor- 
mal values deduced from the barometric minima of threé years. 
I next proceeded to compare wage results with theory. 
Column sixth a table III shows the Mt. Washington obser- 
vations reduced to sea-level by the use of Guyot’s tables as 
contained in his collection of tables, series D, page 33, er ter 
ing the mean temperatures given in column fifth. Column 
‘seventh shows the THVEr SHC between the numbers in columns 
one and six. 
It has been a common opinion among meteorologists that 
Shoes like those shown in column seven result from the 
erroneous assumption that the mean temperature of the air col- 
_ umn between the upper and lower stations is equal to the half 
sum of the temperatures observed at the two stations. In order 
_ sea-level, and the results are shown in column eighth, It will 
be seen that the differences. pay a the numbers in columns 
five and eight range from 0°. 
I next computed the eaeuidn of the Mt. Washington 
observations to sea-level by Ferrel’s tables, published in his 
‘Meteorological Researches, Part III, pages 40-41, and the 
results are shown in column ninth. Column tenth ’shows the 
difference between the numbers in columns one and nine; col- 
umn eleventh shows what must be assuined as the true temmper- 
ature of the air-column in order that the Mt. Washington 
observations reduced to sea-level by Barrel 
a eleven range from 8° to 15°. Some remarks upon these — 
results will be found ona oes page. 
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