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and each little cell is seen to contain a bubble, sometimes larger 

 and more or less flattened by the sides of the cavity, and 

 immovable ; sometimes like the bubble in a spirit-level, moving 

 sluggishly from end to end of a tube-like cell, and sometimes very 

 small, and moving about freely in the cell like a thing of life, 

 perhaps visiting all parts of the cell in turn, occasionally becoming 

 hazy and indistinct, because, passing to a deeper part of the cell 

 the bubble has gone slightly out of focus. If the cell, too, be very 

 small, the bubble, owing to its extreme minuteness, may seem like 

 a mere black speck, and in these cases the motion is exceedingly 

 active, and reminds one still more of a living organism. What can 

 these things mean? For a bubble to move thus freely about, all 

 analogy would lead us to suppose that the cell must be full of 

 liquid, except the bubble spot, otherwise this free motion would be 

 impossible. What then is the liquid, and what does the bubble 

 contain ? Mr. Sorby has paid great attention to these interesting 

 facts, and has clearly proved (ist) that the liquid in most cases is 

 water; (2nd) that the bubble is a vacuum or empty spot, when the 

 movement in the cell is very free ; and (3rd) that the water is 

 frequently saline, and sometimes the cells contain small cubical 

 crystals of salt. Thus we have the astounding fact revealed to us, 

 that in every small fragment of opaque quartz, there are thousands 

 upon thousands of these minute liquid parcels shut up within it, 

 and each containing a vacuous bubble. Again we ask— What can 

 this mean? Can it be that water has had so large a part to 

 play in the formation of this hard mineral quartz ? that granite, 

 which we used to look upon as a molten rock formed in the bowels 

 of the earth, can yet have been formed largely in connection with 

 water? for the quartz combining with felspar and mica to form 

 granite, is literally full of these minute water-cavities. Let us see 

 how this can be in the case of granite, and then other quartz 

 occurrences may prove easier to understand. Mr. Sorby has made 

 many and delicate researches into this subject, and he has found 

 that on subjecting the liquid cavities to heat; first, any minute 

 crystals of salt contained in them are slowly dissolved ; and, 

 second, that when the heat is made sufficiently extreme, the 



