696 



ON CONCRETIONS, SPICULES, ETC. 



[CH. 



and they shew once more how very rough his measurements of the 

 honeycoipb are bound to have been. 



Crystals He outside the province of this book ; yet snow-crystals, 

 and all the rest besides, have much to teach us about the variety, 

 the beauty and the very nature of form. To begin with, the 

 snow-crystal is a regular hexagonal plate or thin prism; that is to 



Fig. 318 a. Snow-crystals, or "snow -flowers." From Dominic Cassini (c. 1600). 



say, it shews hexagonal faces above and below, with edges set at 

 co-equal angles of 120°. Ringing her changes on this fundamental 

 form, Nature superadds to the primary hexagon endless combina- 

 tions of sii^iilar plates or prisms, all with identical angles but varying 

 lengths of side; and she repeats, with an exquisite symmetry. 



Fig. 318 6. Snow-crystals. From Bentley and Humphreys, 1931. 



about all three axes of the hexagon, whatsoever she may have 

 done for the adornment and elaboration of one. These snow-crystals 

 seem (as Tutton says) to give visible proof of the space-lattice on 

 which their structure is framed. 



The beauty of a snow-crystal depends on its mathematical 

 regularity and symmetry; but somehow the association of many 



