OREGON SHORT LINE OGDEN TO YELLOWSTONE. 



129 



Volcanic liills, composed largely of a rliyolite lava, appear to the 



east at a distance of 4 or 5 miles from Gibson siding:. 



On one of the 



Gibson. 



Elevation 4,463 feet. 

 Ogden 151 miles. 



nearer hills of this group there is a rcvy sjnunetrical 

 little cone built of material similar to that which 

 makes so large a proportion of the dark volcanic sand 

 found abundantly in this vicinity. It seems proba- 

 ble that this little cone is the crater from which the sand was blown 

 out and that its eruption marks perhaps the latest chapter in the 

 volcanic history of the district. 



For many miles north from Fort HaU the three buttes in the Snake 

 River plain are visible in clear weather. The westernmost^ or Big 

 Butte, is an old volcano rising 2,350 feet above the plain, or 7,659 

 feet above sea level. East Butte, also a volcano, is 700 feet high, 

 and Middle Butte, an upraised block of basaltic lavas, is 400 feet 

 high. Big and East buttes are ancient rhyolitic volcanoes which 

 existed previous to the outpouring of the fluid basalt that flowed 

 about them, their upper parts rising as islands in this sea of molten 

 rock. They are about 25 and 35 miles from Blackfoot, and Big Butte 

 is 15 miles from Middle Butte and 20 miles from East Butte, The 

 Lost River and Lemhi ranges may be seen behind the buttes. 



North of Gibson there may be a few tepees along the road. At the 

 south end of the bridge over Blackfoot River there is a well-appointed 

 ranch, the home of a prosperous Indian who owns an automobile and 

 has several hundred head of horses and cattle in the hills. 



This bed is also of uniformly high quality, 

 averaging 32 per cent or more of phospho- 

 ric acid, equivalent to 70 per cent or more 

 of bone phosphate. The total quantity 

 of high-grade rock in this main bed, esti- 

 mated for the areas examined by the Geo- 

 logical Survey in five years (not including 

 Montana fields), is approximately 5,000,- 

 OOOjOOO long tons. This estimate includes 

 onJy rock that is believed to lie at minable 

 depths — that is, less than 5,000 feet from 



the surface — but does not include a vastly 

 greater quantity of lower grade rock. 



The ra-w phosphate rock is not readily 

 soluble, so that its action in fertilizing 

 land is very slov, but the so-called super- 

 phosphate, made by treating the pulver- 

 ized rock with sulphuric acid, which the 

 smelters of the West can furnish in large 

 quantity, contains phosphate in more 

 ea.?ily soluble and available form. At 



present, on account of the cost of trans- industry. 



portation to the eastern markets, the de^ 

 mand for western phosphate is confined 

 to the Pacific Coast States, and even here 

 it is in competition with phosphate rock 

 imported from Ocean Island, Of the total 

 phosphate rock produced in the United 

 States in 1914, the Western States fur- 

 nished less than one-half of I per cent. 

 With the growing recognition of the im- 

 portance of intensive agriculture and the 

 consequent need of fertilizers in the great 

 agricultural districts that have passed the 

 period of maximum fertility, the demand 

 for phosphate rock is certain to increase. 

 Although at present the deposits in the 

 Eastern States are more accessible to mar- 

 kets, these deposits are already approach- 

 ing partial exhaustion, so that this rich 

 and extensive western field, already im- 

 portant as a grazing district, is destined 

 to become the scene of another thriving 



92213°— Bull. 612—15 







