28 BOTANICAL SUEVEY OF THE CCEITR D'ALENE MOUNTAINS. 



In such localities small patches of cultivated ground are found at 

 intervals up tlie valley for a distance of 50 kilometers (31 miles) from its 

 junction with the South Fork. Similar small tracts of tilled land exist 

 along a few of the larger tributaries of the North Fork, such as Beaver, 

 Pritchard, and Eagle creeks, and tlie lowermost portion of the Little 

 North Fork. Fear the head of the North Fork are some meadow lands, 

 but access to them is so difficult that tliey are not utilized, except in 

 occasional seasons for their crop of wild hay. 



The soil of tlie valleys varies considerably in its composition and 

 fertility, depending upon the constituents of the rocks from which it is 

 derived. In the upper St. Mary region the mountains are largely com- 

 posed of soft, easily disintegrating, micaceous schists, which have been 

 much worn down. As a result, the outlines of tlie ridges have been 

 softened and the comparatively large quantities of low bench lands 

 formed which constitute so conspicuous a feature of this area. The 

 basaltic outflows of the Tertiary dammed the stream in its central por- 

 tion and created a large lake, which extended toward its head. In the 

 still waters of this lake were deposited the wash from the surrounding 

 micaceous mountains, and to it is due the flat character of the upper 

 part of the stream valley and the enormous quantity of finely com 

 minuted silt mixed with vegetable mold which covers so deeply the bed 

 rock of the bottoms. 



In the middle portion of the valley the soil has received a very large 

 admixture of alkaline elements, derived from the basaltic rocks which 

 border the stream, and, though not of such depth as in the upper part, 

 possesses a greater fertility. The character of the soil in the main St. 

 Mary valley is repeated in those of its tributary streams. 



The slack-water area of both the St. Joseph and the St. Mary have 

 soil of unknown but undoubtedly very great depth, as it represents 

 the accumulation of diluvium deposited over the bottom of Lake Cteur 

 d'Alene during many centuries when it stood at a much higher level 

 than at present. 



The soil in tlie valley of tlie South Fork along its slack-water portion 

 is si miliar to that which exists in the St. Joseph in like situations. 

 There is also a decided element of alkaline deposits due to the teach- 

 ings from the basaltic rocks around Lake Coeur d'Alene and the St. 

 Joseph. 



Above the old Coeur d'Alene Mission the land becomes much less 

 fertile. The mountains adjacent to the valley are composed of highly 

 siliceous rocks, and the soil inconsequence is unduly rich in silica. 

 The same conditions prevail in the valleys of the upper St. Joseph and 

 in the whole North Fork basin. In addition, the mold is rather thin, 

 resting upon beds of coarse gravel and sand, the detritus brought down 

 from the main divides by the feeble glacial action which doubtless once 

 operated there. There is also another cause that has aided to impoverish 

 the soil in the upper part of the South Fork, and it is one that operates 



