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 S. 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 maybe 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 an inch. 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. 
Hour. 
Standard. 
No. 1. 
Attached 
therm. 
Air ther¬ 
mometer. 
Wet-bulb. 
Remarks. 
8 a. m.___ 
30. 150 
30.198 
. 170 
63 
71 
63. 9 
Fair. 
12 in. 
. 100 
69.8 
60.2 
Day fine; Mount Hood covered 
. 140 
.238* 
74 
71.8 
61.5 
with snow, distinctly visible ; 
distant 40 miles. Mount Jef¬ 
ferson also visible; distant 100 
miles. 
8 p. m. 
. 130 
.126 
67 
69 
57.5 
4 a. m. 
. 150 
. 136 
56 
69 
58. 5 
Fair. 
8 a. m. 
.210 
.260 
60 
61 
55 
Do. 
12 in. 
. 140 
.173 
72 
70 
59 
Do. 
4 p. m. 
. 100 
. 150 
78 
79 
66 
Do. 
8 p. m. 
. 110 
.096 
74 
74.5 
61.5 
Do. 
8 a. m. 
.040 
.050 
64 
68 
59.5 
Do. 
12 m. 
.200* 
. 002* 
76 
78 
66 
Do. 
4 p. m. 
. 200* 
. 000* 
86 
86 
68 
Cloudy. 
8 a. m. 
.000* 
.241* 
62 
62 
56.5 
Do. 
12 in. 
.265 
.260 
65 
65 
55 
Fair. 
4 p.m. 
.241 
.240 
69.5 
69.5 
58 
Do. 
8 a. m. 
.260 
.218 
59.5 
60 
54 
Do. 
12 ni. 
.220 
.224 
68.5 
68 
58 
Do. 
4 p. m. 
. 140 
.163 
78 
78 
61.5 
Do. 
8 a. m. 
. 000 
.000 
66.5 
70 
61.5 
Do. 
4 p. in. 
29.990 
30. 029 
86.5 
86 
64.5 
Do. 
8 p. m. 
29. 980 
29. 952 
74 
74 
63 
Do. 
8 a. m. 
30.410* 
30.110 
65 
66 
60 
Do. 
12 m. 
.400* 
.021 
76.5 
76 
61 
Do. 
4 p. in. 
.040 
H68 
83.5 
83 
66 
Do. 
8 p. m. 
. 060 
. 050 
70 
70.5 
57 
Do. 
8 
