136 METEOROLOGY OF THE FIELD EXPLORED. 
during the same period, February 7 to 15, and February 19 to 24, the average temperature of 
Puget sound was about 42°; yet the snow in Clark’s fork increased nowhere more than one 
foot, and that uniformly in the wooded portion of the route. While these are the probable 
conclusions from what is known, the question ought not to be considered settled till further exami- 
nations are made. 
But I have no question that much of the moisture in all the winter months is deposited in rain 
in the mountain passes; and this conclusion must be reached by every observer of the effect of the 
warm rains of the winter on the surrounding mountains, causing in November, in December, and 
in February (I speak of what was observed last winter) large masses of snow entirely to dis- 
appear. The mountains change from day to day. The whole surface of the mountain slopes 
will be covered one day with snow, and the next large portions will disappear, in consequence 
of the genial rains. 
I much regret that Lieutenant Grover did not receive my orders in time to go through the 
pass in March. 
I have thus fully gone into the reasons which have convinced me that there will not be suffi- 
cient snow in this pass to obstruct the passage of cars, and that frequently the pass is practicable 
for horses all through the winter. I believe a wagon-road can be used through that pass with but 
little labor all winter. It seems to me that the conclusions to which I have come, from actual 
observations, are to be drawn; from the extreme narrowness of the mountain range at the pass, 
only about seven and a half miles; from its absolute altitude, only 3,500 feet, being more than 
2,388 feet above Vancouver ; from the open character of the valleys on both sides; and from the 
mild character of the climate of Puget sound, in close proximity, causing much of the moisture 
to be deposited in rain. Should the grades be found good on the western slope, of which I am 
confident, the Snoqualme Pass must furnish the entrance to the sound of the trunk line of the 
northern route; and it becomes important, to satisfy the skeptical, to test thoroughly the ques- 
tions of snow as well as of grades. In the event of the continuation of the survey, I would recom- 
mend establishing a winter post near that pass. At all events, it is unquestionable that no obstruc- 
tions from snow exist in the passes of the Rocky mountains, and of the route of Clark’s fork, 
the Spokane plain, the Columbia and Cowlitz valleys, to Puget sound. 
For more information in reference to this subject I will refer you to Lieutenant Grover’s report 
of his winter trip from Fort Benton to Wallah-Wallah, marked I 36; to Mr. Tinkham’s report, 
marked I 37; and to Mr. Mullan’s’report of his reconnaissance to Fort Hall, marked G 25; as 
also to the letters of Mr. Rice, Mr. Sibley, and Mr. Culbertson, marked I 38, in the appendix. 
No. 1.—MEAN TEMPERATURE FOR EACH OF THE LAST FIVE YEARS. 
Fort Snelling—latitude 45°. 
pe i 5 rs 5 : 
Years. ad . ae 2 u a 2 we a . 
af Bol IRE e000 age fa Een Pe Pa = pe <ereiter i on lige Sco vne 20h fg a 
Oa =a OU = = at a I 8 Nemec De 
a dB ae tT eet ASS cath ng nial aS, alle ce ket | eal rei | ea cet Fl 
13949..| 5.4 | 15.5 | 30.2| 39.7 | 54.8 | 68.2 | 71.6 | 63.8 | 61.5 | 47.2 | 41.6] 8.5] 41.6 | 67.9| 50.1] 9.8] 42.3 
1850..| 14.0 | 18.3 | 24.2 | 37.0 | 55.1 | 71.0 | 76.6 | 74.3 | 60.8 | 49.4 | 33.7] 12.5] 42.1 | 74.0 | 48.0 | 14.9 | 44.7 
1851..| 14.9 | 22.1 | 39.4 | 50.1 | 57.9 | 67.8 | 76.3 | 68.4 | 69.1 | 52.0 | 30.1 | 10.7 | 49.1 | 70.8 | 50.4 | 15.9 | 46.6 
1-52..| 12.7 | 23.1 | 26.5 | 42.1 | 58.2 | 68.5 | 72.7 | 71.0 | 53.8 | 52.7 | 25.5 | 11:8 | 42.3 | 70.7 | 44.0 | 15.9 | 43.2 
1853..| 15.2 | 6.7 | 23.0 | 46.9 | 53.9 | 67.6 | 70.6 | 71.3 | 60.0 | 45,6 | 29.6 | 18.2] 41.3 | 69.8 | 45.1 | 13.4 | 42.4 
WO5A Ce 0.3 |lbeAad 80. Fal ABsBi cece | at cll oe aml des coal tees Ieee en cei |. esl]. oe ec 
Mean.| 10.6 | 16.8 | 29.0 | 44.1 | 56.0 | 68.6 | 73.6 | 69.8 | 61.0 | 49.4 | 32.1 | 12.4 | 43.0 | 70.7 | 47.5 | 13.3 | 43.6 
