No. 3.] AMERICAN ASSOCIATION. 165 



He further described the formation of the bottom of the river, the 

 course and depth of the different currents and the location of the 

 bars, all which indicated that the American channel would never 

 be without water. 



Prof. Tyndall thinks that the depth of the water will deter- 

 mine the course of the chasm channel as the gorge recedes, and 

 the rate of excavation. Prof Holley cited the physical facts 

 which tend to prove that it is the character of the bed of the 

 river, the harder or softer nature of the material to be broken 

 down, that will decide these points. He particularly noticed the 

 fact that the Falls were constantly diminishing in height as they 

 receded, until they reached their present site, where the river 

 makes an acute angle with its former direction. This was neces- 

 sarily the case, because they were receding in the line of the dip 

 of the underlying rock. They are now rising on the dip, and 

 will be 50 feet higher than now when they are two miles up stream. 

 To this bend in the river we owe one of the most beautiful features 

 of the great cataract — the rapids above the Falls. 



Prof. Tyndall speaks of his trip through the Cave of the Winds- 

 and of seeing the shale in it; also of the "blinding hurricane of 

 spray which was hurled against him." Prof. Holley said it was 

 this last circumstance which probably prevented Prof. Tyndall 

 from noticing the fact that no shale v/hatever is visible in the 

 cave. Prof. Holley closed by saying that Prof. Tyndall' s style 

 was so vigorous, animated, and positive that one might be ex- 

 cused if he preferred to read Tyndall's romances rather than the 

 most realistic utterances of many of his brother scientists. 



NEW THEORY OF GEYSER ACTION AS ILLUSTRATED BY AN 



ARTIFICIAL GEYSER. 



By Edmund Andrews. 



This paper stated Bunsen's theory of geysers as illustrated by 

 Tyndall's apparatus, and showed the objections to this theory, 

 the phenomena not corresponding to those of the natural geysers. 

 The theory advocated in Mr. Andrews' paper is, that as the cool- 

 er waters of the surrounding country make their way into and 

 through the caverns of the region of heated rocks, it will some- 

 times happen that the channel of supply will enter a cavern at a 

 point higher than that where the channel of exit leaves it. If, 

 now, this channel of supply has, like many other subterranean 



