870 PROCEEDINGS OF THE ACADEMY OF [DcC. 



ous sandstone (herein referred to as limestone for the sake of conveni- 

 ence) which has a thickness of some 250 to 350 feet. If one digs down 

 through the surface soil a foot or more, almost anywhere on the out- 

 side of the rim, among the angular fragments which have been thrown 

 out of the hole he will come into this silica, and a great number of 

 trenches and several shafts have shown it to continue downward cer- 

 tainly to the solid or rather more or less shattered rock upon which 

 all of the fragmentary material forming the rim rests. One of these 

 shafts, almost at the base of the mountain and near the surrounding 

 plain, is forty-eight feet in depth. However there are, especially on the 

 southern side of the mountain, several dry washes, w'here this almost 

 snow-white silica has been exposed for hundreds of feet in length and in 

 places to a depth of upwards of ten feet. It is difficult to understand 

 how this exposure could escape the eye of any careful geologist making 

 a circuit of the crater. If noticed by him it would certainly seem that 

 he would have examined it and ascertained its nature. Having done 

 this, it w^ould seem that he would have been impelled to make a few 

 shallow trenches at different places around the crater, in order to 

 determine how much of this material there was. Having then proved 

 it to exist on all sides of the crater in enormous quantities, it would 

 seem to me that he could not have explained its presence in any 

 other way than that which we have adopted; especially in view of 

 the fact of there being so much corroborative evidence of even a more 

 convincing character. Briefly, it seems to me impossible that this 

 silica could be produced by volcanic action, or by a steam explosion, 

 and I assume that it could be produced only by the pulverizing effect 

 of an almost inconcei-v ably great blow. It should be stated that the 

 silica on the outside of the rim, and to a less extent underneath 

 the sedimentary material in the bottom of the crater, is plentifully 

 admixed with broken fragments of red sandstone, limestone and 

 white sandstone of all sizes within the limits mentioned and sharply 

 angular shapes. It also should be mentioned that the many cuts 

 and shafts (over fifty in all) which we have caused to be made on 

 the outside of the crater, have shown that the silica carrying with it 

 these broken fragments, especially those of smaller size, has evidently 

 welled out of the crater almost like lifiuid mud, or perhaps, more accur- 

 ately, like flour when it is poured out of a barrel. It is an interesting 

 fact that it often contains innumerable angular fragments of sandstone 

 in which the grains of sand (some pulverized into silica, some whole 

 and unbroken) are no longer coherent, an effect which we have assumed 

 has been produced by tremendous concussion. It would seem that 



