74§ C. R. VAN HISE 



enter the central part laterally ; it will have begun its ascent 

 before it enters the lower part. Therefore a fissure upon the 

 middle of a slope will be very likely to receive water from 

 above, from the side, and from below. But at a certain area of a 

 fissure well up on the slope the water continuously received at 

 the upper side of the fissure will escape laterally at the lower 

 side. This water and that entering the ground below the upper 

 fissure will make its way to the fissure below the valley. But 

 here the level of groundwater is at the surface. Consequently 

 all the water entering this fissure will ascend quite to the sur- 

 face, and issue as a spring. If there be a fissure at the crest we 

 can see that the descending water will go a long way down ; but 

 the waters will nowhere be ascending. If there be a fissure on 

 the slope, both descending and ascending waters will ordinarily 

 be active ; although it is of course recognized that in fissures 

 thus located the conditions may be such that the waters will 

 ascend or descend only. If there be a fissure below a valley 

 where the level of groundwater is at the surface the water will all 

 be ascending; and there will be no descending water. At such 

 places we have springs. Springs do not issue from the tops of 

 mountains, but from slopes and valleys, most frequently the 

 latter. Illustrating this are the Yellowstone Park springs of the 

 Firehole River. The waters which feed the springs fall upon 

 the crests and slopes of the mountains adjacent ; on their way 

 to the valley go deep below the surface, and at the Firehole 

 ascend as hot springs and geysers. The water is driven by 

 gravity due to a considerable head and the lower temperature 

 of the descending column. 



You are all doubtless aware that three theories are main- 

 tained as to the source of the waters which deposit ores. Some 

 hold that the waters doing the work are descending ; others that 

 they enter laterally ; others that they are ascending. The first 

 is known as the descension, the second as the lateral secretion, 

 and the third as the ascension theory. If my argument be cor- 

 rect as to a limit to the zone of fracture, fissures, as well as all 

 other openings, must gradually become smaller and smaller, 



