137 



tion, we may substitute a solid body, choosing one wliicli from its 

 fineness can be diffused uniformly, ami we shall find that a pure 

 salt will, by its polarizing action on this suspended matter, fill its 

 cai-ity quite closely, and make u[) 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, made 

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

 slow evaporation and avoidance of those conditions favoring the 

 production of macles, solid transparent crystals only foi-m. Em- 

 ploying thus many thousands of pounds, or only a few grains of 

 salt, the operation of this law o^ polarization extended to contigu- 

 ous matter 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 strik- 

 ingly presented by them. 



Mr. Charles Stodder stated that Professor Hitchcock, in his 

 " Final Report on the Geology of Massachusetts," 1841, devotes 

 several pages to the subject of claystones. He says : " They are 

 undoubtedly concretions, formed by laws somewhat analogous to 

 those of crystallization. I freely confess, however, that so far as 

 my means of information extend, the subject of concretions is 

 involved in great obscurity." — Report, p. 40G. " When broken, the 

 concretion appears compact and perfectly homogeneous through- 

 out, hi no case have I discovered a concentric or oolitic struc- 

 ture ; nor did the application of strong heat develop it." p. 409. 

 " In a very few cases I have met with a pebble, or a congeries 

 of coarse sand, near the centre of the claystone, which appeared 

 to have been the nucleus around which the particles collected ; 

 but in ninety-nine cases out of a hundred, no such nucleus can 

 be discovered ; although it is undoubtedly true, that there must 

 have been something to determine the particles to a particular 

 centre." p. 410. 



Since Professor Hitchcock's Report, Mr. Stodder was not aware 

 that any observations had been made throwing any light on the 

 origin or structure of these concretions. He exhibited two speci- 

 mens, cut open, — one. No. 1014 of the State collection from Am- 



