ROUTE NEAR THE FORTY SEVENTH AND FORTY-NINTH PARALLELS. 
47 
forty-five miles were two feet and upwards; about twenty miles were four feet and upwards; 
and six miles were six feet and upwards. All the snow was light and dry; it was the accumu¬ 
lated snows of the winter to January 21, deposited in successive layers of a few inches to two 
feet, which have generally lain undisturbed since their fall; and they present little obstruction 
to removal, in comparison with the compact drifted snows of the Atlantic States.” 
From the known effect of abrupt mountains, rising from plains, in increasing the precipita¬ 
tion of rain, it is not probable that less rain falls on the main chain of the Cascade mount¬ 
ains than at Puget sound, hut rather more. 
The mean amount of the winter rain at Steilacoom, on the sound, is 20.6 inches ; the amount 
is nearly the same each winter. The yearly means of the winter rain, in the table of Governor 
S.’s report, are erroneous, though the mean for the winter of several years is correct. 
Snow occupies from ten to twelve times the hulk of an equal quantity of rain. The snow of 
the Cascade mountains is reported to he very dry and light, and the proportion between it 
and rain is probably greater than as 12 to 1. Assuming it to be 12, and supposing the pre¬ 
cipitation on these mountains, during December, January, and February, to be in the form of 
snow, we have at the close of February 20.6 feet of snow. 
The mean temperatures at Steilacoom, Puget sound, from observations at the military post 
there for (four) years, are: 
November, 46°.2 Fahr.; December, 38°.3 Fahr. ; January, 38°.1 Fahr. ; February, 40°.7 
Fahr.; March, 41°.8 Fahr. ; April, 48°.6 Fahr. 
Applying the rule that for every 300 feet of elevation there is a decrease of 1° Fahr., we 
have for the temperatures of an elevation corresponding to that of the summit of the Sno- 
qualme or Yakima Pass—• 
November, 36° ; December, 28°; January, 28°; February, 30°.7; March, 31°.8; April, 
38°.6. 
But from the barren and broken character of the mountain masses east of the Cascade crest, 
the abruptness of the eastern slopes of the main chain, and its great general elevation, 8,000 
feet above the sea, with bare rocky peaks projecting above this height, the highest reaching 
an elevation of 15,000 or 16,000 feet, the temperature of the Yakima Pass must be lower than 
the rule of decrease of temperature for increase of elevation would give when applied to the 
temperature of Steilacoom. The influence of these causes is shown in the meteorological 
report of Lieut. Mowry, by which it will be seen that the climate of the Cascade range and 
the country east of it is very cold. Lieut. Mowry says, page 404, at Chequoss (a pass in the 
Cascade chain 4,000 feet above the sea,) on the summit of the Cascade range, August 9th, 
the thermometer indicated a temperature below the freezing-point, and ice formed to the 
thickness of half an inch. At the same time and place, strawberries were growing in great 
luxuriance and abundance. The Indians informed him that the snow fell there as early as No¬ 
vember, &c., &c. 
Of the 8.69 inches of rain that fell during January at Steilacoom, 5.37 inches fell after the 
26tli; and of the 20.7 inches rain that fell there during the winter (December, January, and 
February,) but 7.74 inches had fallen at the time Mr. Tinkham crossed the Yakima Pass, (21st 
January ;) that is, but little more than one-third of the whole qiiantity that fell during the 
winter. The above investigation is in accordance, then, with the facts as found by Mr. Tink¬ 
ham ; but one-third of the snow had fallen when he crossed. 
Lieut. Grover, in crossing from Clark’s fork to the Coeur d’Alene prairie, between the 19th 
and the 22d of February, found 2| feet of very hard snow for the most part of the way, the 
elevation being about 2,000 and 2,500 feet. The country here is very dry, according to Lieut. 
Mowry. 
It seems probable, from the foregoing investigation, that not less than 20 feet of snow is 
usually to be found on the summit of the Yakima Pass at the close of winter—gradually 
