1826.] vfih hem Varieties, of CmhohfS^C. \&^ 



in ponderable substances, even to the crystalline attraction 

 itself; and that it is in fact the first cause of solidity. Thus the 

 solidification of water commences with the production of fibres 

 or needles, which, by their lateral aggregation and intersection 

 at certain angles, at length produce the solid congeries of crys- 

 tals we term ice. This view does not oppose the sagacious 

 inference of Dr. Young, that a more or less perfect crystalliza- 

 tion is the universal cause of solidity \^ for the tendency I have 

 mentioned would of itself produce an aggregation of matter of 

 one dimension only, viz. that of length ; whereas the tendency to 

 aggregation in several directions,or crystalline attraction, produces 

 the other dimensions of solidity, breadth and thickness.f In the 

 case of the fibres of carbon, crystallization has been exerted to a 

 sufficient extent to give them sensible thickness. Their collec- 

 tion into locks would of course result from the mutual lateral 

 attraction of the fibres, when formed. There are many instances 

 in the mineral kingdom, of two substances belonging to the 

 same mineral-species, or, in other words, to the same material 

 substance, which are very nearly as different from each other, as 

 are these fibres of carbon from the diamond. For example : 

 who, at first sight, would imagine, that the silky, white, light, 

 perfectly flexible, and nearly opaque fibres of amianthus, were 

 identical in their specific nature with the green, transparent, 

 prismatic, rigid, and comparatively hard and heavy crystals of 

 actynolite ? yet such is the fact ; and some mineralogists have 

 accordingly classed them in their systems as varieties of the 

 same mineral. J In this case, the polar attraction appears 

 chiefly to have had place in the production of the amianthus, as 

 in that of the carbon ; whilst the actynolite has resulted from 

 the unchecked influence of crystalline attraction. 



That the slaty carbon of the gas-retorts should be the result 

 of a gradual ana continued process. Dr. Colquhoun appears to 

 consider the most unaccountable part of the pheenomena he has 

 so well detailed. If, however, the solution I have suggested of 

 the principal problem is correct, this gradual accumulation of 

 carbon may be explained in the following manner. Dr. C. 

 states, that the stratified portions of this carbon are quite com- 

 pact in the small. Now is it not reasonable to infer, that each 

 separate stratum is the result of one process of rapid solidifica- 



* See his Ijectures on Natural Philosophy, vol. i. p. 627. 



t Some evidence, I think, that this tendency to linear arrangement, or to polarization, 

 is the first power operating on solid particles of matter towards their aggregation, is 

 afforded by the facts pointed out by Sir E. Home and Mr. Bauer, that the most minute 

 fibres in nature with which we are yet acquainted, those constituting the muscles and 

 nerves of animals, consist each of a simple row of attached globules ; and that the com- 

 mencement of the operation by which coagulated blood becomes vascular, is the attach- 

 ment together in one direction of its constituent globules, forming such fibres. 



t See, in particular, Prof. Mohs's Treatise on Mineralogy, translated by Haidmger, 

 vol. i. p. 388. 



