GEOLOGICAL SURVEY OF THE TERRITORIES. 



147 



in assisting: ns 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 part is com[)osed of broken bits of geyserite. 

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

 doubt tbat many of the springs are at the boiling-point, (199<^.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. 





At the lower end of the basin the Fire-Hole Eiver 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 foot 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 Springs ; their general elevation is 

 7,296 feet. These springs were described at length in the report for 

 1871. The illustration (Fig. 3Ga) by Mr. Elliot shows one of the princi- 



