GEOLOGICAL SURVEY OF THE TERRITORIES. 



147 



in assisting us to conclusions upon the subject. My space here is too 

 limited to do more than refer to it. 



The area of the lower geyser-basin is about thirty square miles, and 

 the valley seems to be underlaid by a sedimentary,' probably Post-plio- 

 cene, formation of which ])art is com[)Osed of broken bits of geyserite. 

 The highest temperature that was recorded is 198° F., but there is no 

 doubt that many of the springs are at the boiling-point, (1990.5 F.,) it 

 being impossible to determine it on account of the spoutiug of the water. 

 The general elevation of the lower basin above sea-level is 7,275 feet. 







1 





At the lower end of the basin the Fire-Hole River is joined by Fairy 

 Fall Creek, at the head of which there is a beautiful fall called the Fairy 

 Fall. This fall is 250 feet high, and the water falls into a beautiful 

 basin at the toot of a cliff. From the mouth of this creek to the mouth 

 of Iron Spring Creek, at the lower end of the upper geyser-basin, the 

 distance is five and a half miles in a bee-line. Between the two there 

 IS a large group of springs that can be included in neither, and to which 

 we gave the name of the Half-Way Si)rings ; their general elevation is 

 7,290 feet. These springs were described at length in the report for 

 1871. The illustration (Fig. oO«) by Mr. Elliot shows one of the i»rinci- 



