602 METEOROLOGICAL OBSERVATIONS. 
BAROMETRIC AND METEOROLOGICAL OBSERVATIONS, MADE DURING THE SURVEY OF A LINE FROM 
COLUMBIA BARRACKS TO FORT COLVILLE, AND THE RETURN; BY LIEUTENANT 8S. MOWRY, U. S. 
ARMY. 
Comparison of barometers.—The mercurial barometers are designated as “standard,” ‘No. 1” 
and “No, 2;” the first of which was left at Columbia Barracks and regularly observed for nearly 
five months. The mean of its readings for this period gives quite accurately the known altitude 
of Columbia Barracks above the sea, and it may therefore be taken as without zero error, though 
no comparison of it with an absolute standard exists. Barometer ‘No, 1” reads so nearly with 
this “standard” from July 1st to July 18th, the time of departure, that no zero correction need be 
introduced. This barometer is carried nearly to Fort Okinakane, and may be used for all the 
determinations of altitude. Barometer ‘‘ No. 2” differs considerably at Columbia Barracks from 
either, and continues to differ as far as it is carried, which is to camp 28, “on the north branch 
of the Columbia,” by between two and three tenths of aninch. It is doubtless nearly so much in 
error ; and as its readings do no appear necessary to any determination, they are not given in the 
tables. 
The aneroid barometers, Nos. 9445 and 7992, are compared at Columbia Barracks and used 
after the mercurial instruments are broken. Their readings are quite irregular, and Lieut. Mowry 
places little confidence in them. When they have an approximate accuracy or possible value, 
they are transcribed with the journal, but no altitudes are computed from them. At the return of 
the party they differed from the ‘‘standard” by very large measures. 
Barometers “‘ No. 1” and ‘‘No. 2” were syphons. It does not appear whether the ‘“ standard” 
was an open cistern, (brass,) or Alexander’s mountain barometer, the vernier of which is adjusted 
to a glass column only. The correction for temperature is somewhat less in this case than for an 
open cistern with brass scales. The correction for brass scales is, however, applied to all the 
readings of the barometer retained at Columbia Barracks as the “standard.” 
Barometric Readings at Columbia Barracks. 
Date. Hour. Standard. No. 1. Attached | Air ther- | Wet-bulb. Remarks. 
therm. | mometer. 
July PALER ihe ere 30. 150 30, 198 63 63:59:45] 2.8 eater Fair. 
12 i eseewene . 160 . 170 71 69.8 60,2 | Day fine; Mount Hood covered 
ADs ios wees . 140 . 233+ 74 71.8 61.5 with snow, distinctly visible ; 
Sp a00 eee ae ere . 130 . 126 67 69 57.5 distant 40 miles. Mount Jef- 
ferson also visible; distant 100 
miles. 
3 . 150 . 136 56 69 58.5 Fair. 
. 210 . 260 60 61 55 Do. 
. 140 .173 72 70 59 Do. 
. 100 . 150 738 et Dae 66 Do. 
aL) . 096 74 74.5 61.5 Do. 
4 . 040 . 050 64 68 59.5 Do. 
. 200* . 002* 76 78 66 Do. 
. 200* . 000% 86 86 68 Cloudy. 
5 . 000* . 241* 62 62 56.5 Do. 
. 265 . 260 65 65 55 Fair. 
.241 . 240 69.5 69.5 58 Do. 
6 . 260 . 218 59.5 60 54 Do. 
. 220 . 224 68.5 68 58 Do. 
. 140 . 163 78 78 61.5 Do. 
7 000 . 000 66.5 70 61.5 | Do. 
29, 990 30, 029 86.5 86 64.5 Do. 
29, 980 29, 952 74 74 63 Do. 
8 30. 4104 + 30, 110 65 66 60 Do. 
. 400° . 021 76.5 76 61 Do. 
. 040 (68 83.5 83 66 Do. 
. 060 . 050 70 70.5 57 Do. 
