44 



THE MUSEUM. 



Mr. Wilmore Newell of Primj^jhar, 

 Iowa is doing some of the best work 

 in X Ray photography we have seen. 

 Some sample photos he has sent us, 

 show a very high grade of vvork. 



Fracture and Displacement of 

 Rocks. 



BY C. O. ORMSBEE, MONTPELIER, VT. 



In geological study one is often at a 

 a fault because he has neglected to 

 study the apparently insignificant 

 forces which Nature often uses to ac- 

 complish her designs. Bearing this in 

 mind, I will endeavor to describe some 

 of the methods used in breaking rocks, 

 and in moving them from their resting 

 places. 



Whoever examines the rocks of New 

 England cannot fail to notice that most 

 of them are covered, to a greater or 

 less extent, with various kinds of moss, 

 none of which have any commercial or 

 economic value, so far as we have yet 

 been able to discover. Nevertheless 

 this moss plays a two-fold part in 

 geology, or rather, in physiography. 

 The first and most apparent-part is the 

 formation of new soil; but, as this is 

 foreign to the subject of this article I 

 shall enter into no description of the 

 process in this issue of the Museum, 

 although I hope to make it the subject 

 of a future paper. 



The second purpose of the moss is 

 to assist in breaking the rocks, which 

 is the first step towards a final pulver- 

 ization. 



It will be noticed that the moss, in 

 most instances grows in little patches. 

 Very rarely does it cover the whole 

 surface of the rock. Detach it and 

 the surface of the rock will be found 

 to be moist. In fact the rock beneath 

 the moss is, as far as its nature will 

 permit, -'water-soaked." More than 

 this, the rock will be found to be of 

 unequal hardness — being softest where 

 the moss is thickest, and where, in 

 consequence of a greater amount of 

 covering, it is most thoroughly satu- 

 rated — and hardest in those places 



which are exposed to the sun's rays. 

 Moreover, the moss shelters the rock 

 to some extent from the extremes of 

 heat and cold; and this, combined 

 with the fact that the rock is of differ- 

 ent degrees of hardness, and is also 

 unevenly saturated causes frost to act 

 unevenly upon the rock. The result 

 is, that sometimes a tiny crack appears 

 upon the surfact of the rock. This 

 crack may be smaller than the finest 

 hair. Still a drop of water finds its 

 way into it, and freezing, forces the 

 rock apart, and, in time the rock is 

 broken. And not only this, but, as 

 the crevice becomes wider, the frost 

 has a better leverage, and the two 

 pieces may be forced several feet 

 apart. 



And while I am writing about it, let 

 me briefly describe a granite rock up- 

 on which I played when a small boy. 

 In shape, this rock resembled the roof 

 of a house. It was about seven feet 

 long, four feet wide and three feet 

 high; but from one side a large slab- 

 had been split, — doubtless by this 

 process. This slab remained in posi- 

 tion, and I remember that, in those 

 days I could barely squeeze my hand 

 into the crevice. At the present time 

 a distance of eighteen inches separates 

 the smaller rock from its parent. The 

 rocks have been forced apart by the 

 action of water which found its way 

 into the crevice, and, increasing in 

 volume as it congealed, exerted a 

 powerful pressure upon them. 



Besides this, there are many other 

 forces by means of which rocks may 

 be broken. I have several times seen 

 a large tree fall upon a rock and break 

 it into fragments. This is frequently 

 the case with the softer rocks and oc- 

 casionally, even with granite. In my 

 rambles through the fields I frequently 

 find rocks that have evidently been 

 broken by this means. 



Again, it must be remembered that 

 this country was formerly covered with 

 a dense forest. In many instances the 

 land was cleared by cutting the trees 

 and burning them as they lay. It was 



