CHEMICAL SCIENCE. 299 



mny substitute a solid body, choosing one, which, from its fineness can be 

 diffused uniformly, and we shall find that a pure salt will, by its polarizing 

 action on this suspended matter,/;'// its cavity quite closely, and make up its 

 true solid crystal in part of clay, Prussian blue, or other bodies. Ranging 

 through the ordinary salts, cooling from solutions, or the melted state, maclo 

 crystals will be obtained almost constantly, while in all cases of slow eva- 

 poration and avoidance of those conditions favoring the production of 

 inacles, solid transparent crystals only form. Employing thus many thou- 

 sands of pounds, or only a few grains of salt, the operation of this law of 

 polarization extended to contiguous waiter is seen, and in the experiments 

 alluded to, it was shown that its modified and more complex action gave 

 beautiful results. Skeleton crystals, such as sublimates, and snow-flakes, 

 and frost-work may be assumed to be solid crystals, at the instant of their 

 formation : the vapor, or air, being polarized to fill the vacancies, which 

 afterwards appear, gives the beauty and variety so strikingly presented 

 by them. 



Mr. Stockier called attention to forms of clay concretion or segregation, 

 which he saw some years since in Windsor, Ct. 



On the bank of the Farming-ton River, was a bold, nearly perpendicular 

 bluff of the Connecticut valley clay, stratified in horizontal layers of from 

 half an inch to an inch, and perhaps two inches in thickness. The divis- 

 ional planes between the strata were indurated, perhaps one sixteenth of 

 an inch 'thick, and somewhat harder than the mass of the clay. Exposed 

 to the elements the softer clay had been washed out between the hardened 

 divisional planes, to the depth of one or two inches. Extending from one 

 hardened plane to another, were cylindrical concretions of from one fourth 

 to three fourths of an inch in diameter, at various distances apart. The 

 bluff, seen in front, presented the appearance of small shelves supported 

 by innumerable small columns, many of which had a small hole through 

 the centre. They looked as if they might have collected about the root- 

 lets of plants, but it is questionable whether roots would penetrate clay 

 to the depth of ten or fifteen feet, or their direction would always be ver- 

 tical. 



The columns undoubtedly were not lime and clay like the clay-stones, 

 but mcrelv indurated clav, as none of them could be found at the base of 



K * ' 



the bluff, the fallen ones having decomposed. 



OX THE REACTIONS OF THE ALKALINE SILICATES. 



T. S. Hunt, Esq., of the Canadian Geological Survey, communicates 

 the following memoranda to Professor Dana of Silihnan's Journal. He 

 says : I have lately been engaged in studying the reactions of the al- 

 kaline silicates with the carbonates of magnesia and iron. We have long 

 known that carbonate of lime and alumina have the power to remove 

 silicate from a solution of soluble glass ; and I find that when a mix- 

 ture of silica and carbonate of magnesia is boiled with carbonate of soda, 

 the silicate of soda at first formed is decomposed by the marrnesian car- 

 bonate and the regenerated carbonate of -joda is enabled to dissolve a new 



