134 METEOROLOGY OF THE FIELD EXPLORED; 



Comparison often clays before reaching the summit with the corresponding temperature periods 

 eastward : 



Between Fort Benton and the Rocky mountains 2d to 11th January, -f24 



Pembina, Red River valley &quot; 3d to 12th +5 



Fort Snelling 4th to 13th + 7.7 



Fort Ripley 4th to 13th + 3.9 



Lacquiparle, Minnesota 2d to 12th &quot; + 13.6 



Fort Ridgeley 4lh to 12th + 8.5 



Madison, Wisconsin 4th to 13th +17.5 



Pittsburg 4th to 13th &quot; +32.4 



Rochester 4th to IGth &quot; +30.4 



West Point. 5th to 16th +32 



Amherst, Massachusetts Cth to 16th &quot; -f27.4 



Oldtown, Maine 6th to ISth &quot; + 14.2 



Albion Mines, Nova Scotia Gth to ISth &quot; + 20.4 



Mean 2l.4 



24.0 



2.G 



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 Black foot 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 twenty-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 h.irdly 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, 



