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. 
B sos s cages DT RRN Sh « QUA eco a ee aaah esos ae a 29.466 
y. uou m DELL a Aa i a E E E E hes adus eM 29.483 
AUgest.. no a e —————— — 29.431 
September ..... MOL NULLO keen A E EE mp bm a epee 29.474 
DEESSET III di cos uusccanevec cavdicecee 29.538 
OMNEM a EEE ee E AN APE ee 29.601 
December...... OO; sds vp Lus IE ESL eu. xcu MEE wed ak aA 29.508 
Janpary .. ...- EL DE REEE DE WET E ISOUU REOR 4% pl inate dais 29.577 
Kebruary....... GD. 5 ihe CRANE RAMUS AR HUMOR: € N aie eile 29.507 
Nun. i.i. QO. ILLI recessed eret uaa d MES 29.459 
RO ss eas ae G0. 555 4s Ss Re eee EIS 29.444 
Mayr itar sue Ss. EE I EAD E E RACE MER E EIUS «d sser MOOR 
SAEN EE EEE a Ta PAPE E sna A E NE ETE E E e bn. NEATIS 
iui nemis En GO cadens ew dd duh duhidel qub sio Mn iv api dia e ii 29.491 
Sr. Louis, September, 1854. 
