134 On the Law of Symmetry^ 



still, AS soon as the temperature falls to the requisite degree, 

 spicula symmetrically related to each other instantly make 

 their appearance. These presently become so numerous as to 

 constitute laminae, which, in their turn, decussate each other 

 symmetrically, and become the frame- work of a tissue so essen- 

 tially crystalline, that even after the intimate symmetry of the 

 mass has been very much broken up by the freezing and ex- 

 panding of the last portions which congeal, still, when inquired 

 into by the aid of polarised light, it declares itself to pos- 

 sess a crystalline structure. The element whose tendency to 

 assume a symmetrical structure, when permitted to pass from 

 the liquid to the solid state, is thus shown by the ordinary phe- 

 nomena of congelation, exists also in the atmosphere, from 

 which it is occasionally precipitated in solid masses. Now, of 

 these also, it is to be remarked, that always, except in cases of 

 great atmospherical agitation, their forms are of most exquisite 

 symmetry. Whether we inspect the hoar-frost which fringes 

 the leaves in a winter morning, or the snow which covers the 

 ground, we shall equally find matter of a beautifully crystaUine 

 structure. And this will, I presume, be assented to by all, that 

 the greater the stillness in which the atmospherical aggregation 

 of the aqueous particles takes place, the more perfect will be the 

 resulting symmetry. 



But while it is thus obvious that there is some power which 

 produces symmetry, it will also be perceived that there is some 

 power which circumscribes and limits it, so that forms only 

 which belong to one series do constantly result. Thus, where 

 entire individuals may be developed, as, for instance, when 

 aqueous particles aggregate together from solution in the atmo- 

 sphere, the lineaments of a hexagon are constantly to be detect- 

 ed in the snow-flakes that result ; and whatever be the particu- 

 lar form of each particular snow-flake, this may be affirmed of 

 them all, that they may be inscribed in a circle. In hoar-frost, 

 in like manner, and masses of ice (in which, either from con- 

 nexion with foreign bodies, or with each other, a complete insu- 

 lation of individuals, and consequently a complete evolution of 

 form, is prevented) angles of 60°, and forms known to belong 

 to the same crystallographic series with the six-sided table, are 

 alone to be met with. In plants also, in which what may be 



