452 PARTIAL RESULTS OF EXPLORATION. 
There will be no difficulty as to water. It will be deficient at points on the broad plateau be 
tween the Milk and Missouri rivers, but by aqueducts it can easily be supplied. The lakes on 
the Grand Couteau will also furnish the means of supplying any deficiency from the Grand 
Couteau to a point south of the Miniwakan lake. But our observations go to show that there 
need be little apprehension of a deficiency here. On the Great Plain of the Columbia, I appre- 
hend no deficiency in the © spp of water; the whole country abounds in lakes and small 
streams. 
Our observations and inquiries go to show that the average depth of snow east of the mount- 
ains to the Missouri does not exceed one foot. Two feet is an extraordinary depth, and the most 
experienced voyageurs in that country have never been detained a single day in travelling by 
snow. ‘The most they have been compelled to do was to lie by till the storm was over. 
In the Rocky mountains, and on the line of Clark’s fork, the snow is hardly ever deep enough 
to prevent the Indians travelling with their families on horseback all through the winter: one 
foot is a common depth, and three feet is a very extraordinary depth, in the Rocky mountains. 
Last winter the average on the several passes was less than one foot. The winter before—the 
winter of greatest snow for many years, as shown by the unprecedented rise of the rivers in the 
following spring—the depth was three feet. 
On the Plain of the Columbia, in the lower Columbia valley, and on the route thence to the 
Sound, the snow is inconsiderable. 
On the route of the Yakima and the Snoqualme Pass, there is but little snow for some forty 
miles eastward from the Sound, and for more than a hundred miles up the Yakima valley. On 
the pass itself, there was, the last winter, on the 20th January, six feet of light snow for some 
six miles. The depth, I am of opinion, did not much increase subsequently ; but to test the ques- 
tion fully, further observations ought to be made, 
For more full information in reference to the forest growths, supply of sleepers, and building- 
materials for the road, and for the supply of water, I will respectfully refer you to Chapters V 
and XII of my report. Chapter V treats of the section east of the Rocky mountains, and Chap- 
ter XII of the section west. For the depth of snow, I will refer you to Chapter XIV, and to sub- 
reports I 35, I 36, I 37, and I 38. 
The observations for heights having been lost, the discussion of the several altitudes cannot be 
made till they are recovered; and for longitudes, the only dependence at this time, and before 
further observations are made, will be to adjust the odometer line in connexion with the latitudes 
between Nicollet’s Lake Jessie and Wilkes’s Wallah-Wallah on a projection, and ascertain a par- 
ticular longitude by protraction; I am confident the result will be good. 
The general map indicates lines to be examined, and for full information I will respectfully 
refer you to Chapter XVIII of my report. I will, however, give the following condensed state- 
ment of examinations which I will recommend to be made: 
1. More detailed examinations of the line of the lower Columbia and of the line of the Sno- 
qualme Pass, to determine which is most practicable. 
2, Careful examinations of Lewis and Clark’s, Cadotte’s, and the Northern Little Blackfoot 
Passes, and their several approaches, to determine as to which is most practicable. If Lewis 
and Clark’s or Cadotte’s Pass be preferred to the Northern Litle Blackfoot, examinations to be 
made to determine the practicability of passing directly from the Blacktoot trail to Clark’s fork. 
This proving impracticable, or the Northern Litde Blackfoot Pass proving preferable, then a 
careful comparative survey to be made of the line of the Bitter Root and the line of the Jocko. 
More careful observations of the southern portion of Clark’s fork to be made, to determine 
whether the road shall pass to the Spokane from the western or the eastern side of the Pend 
d’Oreille lake. 
Examinations to be made to determine the practicability of connecting the Rocky mountain 
passes with Council Blu through the Black Hills, and also to determine whether these passes 
