134 
METEOROLOGY OF THE FIELD EXPLORED. 
Comparison of ten days before reaching the summit with the corresponding temperature periods 
eastward : 
Between Fort Benton and the Rocky mountains 
Pembina, Red River valley. 
Fort Snelling. 
Fort Ripley. 
Lacquiparle, Minnesota. 
Fort Ridgeley. 
Madison, Wisconsin. 
Pittsburg. 
Rochester... 
West Point.... 
Amherst, Massachusetts.. 
Oldtown, Maine. 
Albion Mines, Nova Scotia. 
.2d to 11th January, 
-1-24° 
,3d to 12th 
U 
+ 5° 
,4th to 13th 
u 
+ 7°.7 
4th to 13th 
it 
+ 3°.9 
.2d to 12th 
a 
+ 13°.6 
4th to 12th 
u 
+ S°.5 
.4th to 13th 
n 
+ 17°.5 
. 4th to 13th 
u 
+ 32°.4 
.4th to 16th 
u 
+ 30°.4 
.5th to 16th 
u 
+ 32° 
6th to 16th 
u 
+27°.4 
.6th to 18th 
cc 
+ 14°.2 
.6th to 18th 
u 
+20°.4 
Mean 
21°.4 
24°.0 
2°.6 
Mr. Tinkham met with no snow on the Marias Pass till the day aftercrossing the divide, October 
21st, when a few inches fell. His course back was by the Little Blackfoot trail, and the snow 
was about an inch or two deep in the divide. On the southern Nez Perces trail over the Bitter 
Root mountains, the snow was -six feet deep for one hundred miles or more. This trail is from 
one hundred to one hundred and fifty miles south of the railroad line. This depth of six feet oc¬ 
curred in ^December, when there was but twelve to fifteen inches in the passes of the Rocky 
mountains, the divide being at least 7,500 feet high, and it covered a much greater extent of 
country. The snows are of an entirely different character, being wet and compact, and the tem¬ 
perature much milder than in the Rocky mountain divide. 
Mr. Tinkham’s passage of the Cascades on the 21st January furnishes the only observations we 
possess as to the depth of snow in that range. Crossing after mid-winter, he found for six miles 
the snow six feet deep, with occasional depths of seven feet, as also of four feet. For twenty 
additional miles the snow was from four to six feet deep, and for twenty-five miles more, two to 
four feet. Of this depth one and a half to two feet fell on the night of the 19th and 20th January, 
so that in mid-winter the snow was but four to five feet deep in the divide. This snow was very 
light, in layers of one and a half to two feet, and Mr. Tinkham is of opinion that the rains of 
February would tend to make the snow more compact, so that the depth would diminish, notwith¬ 
standing more snow fell, making the pass practicable in March. I will particularly refer you to 
his report for the details of his interesting trip, and the conclusion which his judgment has reached 
in this question. I discredit the evidence of Indians, except when they have actually made per¬ 
sonal observations. The Indians cannot be competent witnesses as to the snow being six or ten 
feet deep in one place, or twenty to twenty-five feet in another, lying in their lodges as they do 
all winter, and seldom ever using snow-shoes at all. Early in January the Indians at the Sno- 
qualme falls were of opinion that the snows in the pass were twenty to twei^-five feet deep, 
where, according to Mr. Tinkham’s measurements, making the allowances for the intermediate 
fall of snow, it could not have exceeded four or five feet. Among the Yakimas, Mr. Tinkham 
was hardly able to get shoes enough for his party, and none were found among the Snoqualme 
Indians on the other side. It was with difficulty he could get guides, and was in consequence 
detained two days; yet he was assured by them that the snow in the pass would only be up to, 
