MONTHLY BAROMETRIC MEANS AT ST. LOUIS. 
93 
The aneroids are certainly very unreliable; but within the limited range of my observations, 
(between twenty-nine and thirty inches,) they performed well and corresponded pretty accu¬ 
rately with the fluctuations of my own barometer. 
In calculating elevations from barometrical data, it seems best not to compare isolated observa¬ 
tions made on the same day, or at the same hour, but to refer the observations made in the 
field (or the mean of several if they can be had) to the monthly means of the stationary 
barometer. I add, therefore, my monthly means for the last fourteen months. But the ob¬ 
servations made west of the Rocky mountains cannot be referred to my barometer at all. 
It is hardly necessary to add—what everybody who is in the habit of observing the barometer 
knows—that observations made in the forenoon, principally from 8 to 10 o’clock a. m., are gen¬ 
erally higher, and those in the afternoon, principally between 2 and 4 o’clock, are mostly lower 
than the average of the day. The noon observations come nearest the mean of the day. 
The barometer—at least in the Mississippi valley—is usually highest with westerly and north¬ 
westerly winds, and lowest with southerly and southeasterly winds. It is mostly higher, but 
much more irregular, in winter, and lower but more regular in summer. 
BAROMETRICAL ELEVATION OF BAROMETER E., AT ST. LOUIS, 482 FEET ABOVE THE GULF. 
Table of monthly barometrical means at St. Louis , corrected for temperature. 
June. 1853. 
Juiy.do.. 
August..do.. 
September.do.. 
October.do.. 
November__ .do., 
December.do.. 
January.1854, 
February.do. 
March.do.. 
April.do., 
May.do.. 
June.do., 
July.do.. 
. 29.466 
. 29.483 
.. 29.431 
. 29.474 
.. 29.538 
. 29.601 
. 29.508 
.. 29.577 
. 29.507 
.. 29.459 
.. 29.444 
. 29.334 
. 29.418 
. 29.491 
Dr. GEO. ENGELMANN. 
St. Louis, September, 1854. 
