1905.] NATURAL SCIENCES OF PHILADELPHIA. 901 



siderable amounts to remain imder them on the final deposition of the 

 mixed masses of material in the rim of the hole after their expulsion. ■ 



The Crushed Sandstone at Its Upper Contact with the Lime- 

 stone AND THE Shattered Cliffs around the Hole. 



The author desires particularly to call attention to these features of 

 the walls surrounding the hole. It is very distinctly marked. It is 

 unqestionably due to excessive pressure. If this cone and crater are 

 due to any form of volcanic action, it is difficult to see how this crush- 

 ing occurred. The sandstone is amply strong to carry its over-biu"den 

 without crushing ; in fact before the general erosion of this country it 

 probably carried many hundreds or thousands feet more without crush- 

 ing and pressure from above or below as equal in its crushing effects. 

 Then suppose pressure to gradually accumulate and the overlying 

 strata to bulge up into the dome of which the present cone is the base; 

 there could be accumulated but little excess of pressure to crush the 

 sandstone during this rise, as it would be as free to go up under the 

 weight of its overlying strata as it was to support them quiescent, for 

 such motion would be very slow. Then comes the giving way and the 

 explosion, and the result to the remaining rock left around the hole is a 

 relief from pressure and not an increase of it. It is difficult under any 

 of these conditions to imagine any force tending to crush this sandstone 

 and shatter the surrounding walls in the manner that they are shown 

 to-day. It is difficult to discuss the steam explosion theory, for the 

 reason that nobody has ever seen one or known with certainty of any 

 such action, except the blowing off of the tops or sides of ordinary 

 volcanoes in activity in this manner, which is as different as possible 

 in its effects from the so-called maars. There are a lot of holes, not 

 very uniform nor congruous among themselves, which, for want of a 

 better explanation of their formation, have been ascribed to this source, 

 and to which class Coon Butte has been assigned by Prof. Gilbert, as 

 the result of his investigations. This crushing of strata and shattering 

 the walls is, however, the direct and obvious result of the blow of a great 

 projectile. There is almost instantaneously generated an overwhelming 

 pressure deep down in the rocks, tending to lift the surrounding strata 

 at 1,000 or more feet per second. The great weight and inertia of these 

 strata oppose an enormous obstacle to this sudden movement, and the 

 crushing strains developed crush up the weakest rock until the necessary 

 yielding and velocity have been imparted to the overlying strata. The 

 shattered cliffs and upraised rim show the rock started from its position 

 and in partial transition from the hole, from which it would have been 



