Snake Plains of Idaho. Mt 



of broken down craters, the largest of which, 

 Big Butte, rises about 600 meters (2,000 feet) above the plain. 

 Some of canons of Big Butte support a growth of Douglas fir 

 and Murray pine. The lava flows present great diversity 

 of form; elevated ridges of rough rock irregularly fissured and 

 with jagged edges alternate with smooth, Hat domes, suggest- 

 ing giant bubbles; nearly level stretches marked by wavelets 

 and ripples which bend and double, spread out as if just 

 escaped from a seething, tumultuous caldron, while in many 

 places the thick crust has fallen in, leaving deep pits of 

 circular or elliptical outline, exposing the mouths of dark 

 caverns that extend to unknown depths and furnish homes to 

 owls and bats and a multitude of nocturnal animals. Tins 

 black lava or basalt overlies an earlier flow of porphyrin. 

 trachite, grav in color and much less firm in texture. I he 

 Great Shoshone Fall, commonly known as the "Niagara ..f the 

 West," results from the cutting down of the river bed through 

 the hard basalt to the softer trachite below. 



In summer the heat is excessive, the thermometer frequently 

 reaching 110° in the shade, while in winter the snow covers 

 the ground, and icy winds sweep over the plain. The forms 

 of life which inhabit the region, therefore are such as can 

 endure great heat during the season of reproductive activity, 

 and can avoid the cold of winter by migration or hibernation ; 

 or if they remain active throughout the year they are hardy 

 species, able to withstand great extremes of temperature and 

 humidity. 



Most of the rivers which flow down through the mountain 

 valleys disappear on reaching the plains, and the greater part 

 of the water which reaches Snake River does so by subter- 

 ranean channels. Hundreds of springs pour their waters into 

 the lava canons of Snake River, usually at or near the bottom, 

 and many of them are of great size. In winter their tempera- 

 ture is considerably higher than that of the river. < rayfislj, 

 identified by Mr. Walter Faxon as Astacus gambelln Girard, 

 abound in these warm springs and are much sought after by 

 (Procyon lotor?) and a small shell identified by Dr. 



