162 THE MICROSCOPE. Nov. 



the recesses of remote granite mountains, or, generally, 

 its action was most strongly exerted in these localities. 

 The fact, whatever its interpretation, remains, and though 

 it did not lie in the particular line of our investigation, 

 it is suflBciently interesting to be recorded as a bye-pro- 

 duct. 



The size and shape of the grains tell us very little of 

 their previous history. If they are much rounded, w^e 

 infer much tossing about the world, and a long journey 

 from their original home to their temporary resting 

 place in the sandstones. One would think that the smaller 

 grains would naturally be the most rounded, from long 

 tear and wear in transit from place to place. That, how- 

 ever, is not so. So far as the Elgin sandstones are con- 

 cerned the very reverse is the case. The larger grains 

 are almost invariably the more rounded. The reason, 

 I think, is evident. The larger grains from their weight 

 are more apt to be rolled along by the force of water, 

 while the smaller are, so to speak, floated along, and 

 hence do not suffer so much attrition from contact with 

 other grains. So much for the adventitious characters 

 of our sand grains. They practically tell us very little 

 about their previous history. 



Fortunately for our purpose quartz grains are not al- 

 ways homogeneous, and when we come to look at them 

 closely with the microscope a whole vista of possibilities 

 of learning something of their life history at once bursts 

 on our astonished vision. If we look at quartz grains 

 with a moderately high power of the microscope we find 

 that many of them contain numerous little objects — some 

 of them beautifully shaped, some of them beautifully 

 colored, all of them essentially wonderful. These are 

 what we call inclosures or inclusions in the quartz. They 

 are sometimes other minerals in their regular crystal- 

 line forms enclosed in the quartz. Let us make certain 

 what an inclusion really means. — Concrete examples of 



