206 



Marvels of the Universe 



the two thousand crystals which he has photographed were put into one solid'mass they would 

 only occupy a cubic inch. 



Roughly speaking, we may distinguish feathery and solid crystals. The first grow quickly and 

 are characteristic of low-lying storm clouds which are not very cold. In the most open forms 

 there are the six distinct rays just joining at the centre (see the first illustration on page 204), each 

 of which otherwise develops independently, but symmetrically, so that we get what are practically 

 six crystals growing together to form new elaborate and delicate shapes. When the centre is at 

 first a little more solid and the connection between the rays at their bases greater, we get probably 

 the most effective of all the types of snow crystals such as are shown most beautifully in the full- 

 page illustration. The compact crystal, on the other hand, is said to come, in some cases, from a 

 height as great as eight miles, where great blizzards arise, and grows slowly as it is blown about, 

 perhaps for days, adding gradually to its size and weight, until it finally comes to earth. 



Some examples of the very solid kind of crystal are given in the illustrations on page 205. They 



SNOW CRYSTALS. 



Thr 



further variations 



The 



entral 



example shows the 



rays but slightly decorated. 



may grow and continue to retain their very simple though accurate hexagonal outlines, or their 

 angles may develop. In this case two things can happen ; either the solid type of crystal will be 

 reproduced in their branches, as shown on page 208, which are occasionally quite elaborate, or they 

 may depart from their original method and become open and more delicate. In this way we may 

 get the forms which we have already alluded to with the solid centre and lace-like branches shown 

 in the plate. 



Not the least beautiful feature of the crystals, apart from their form, is the internal structure 

 caused by the inclusion of tiny air-bubbles, and these also enable us to see how the growth of the 

 crystal has gradually taken place. 



The marvellous regularity with which the crystals increase in size in the six directions is shown 

 by these bubbles. Take, for instance, the lower right-hand crystal shown on page 205. Within each 

 side is a curious and complicated figure, at the top of which is a little four-rayed object with a dot 

 in the centre. Each of the six is practically the counterpart of the other. It will be seen, however, 

 that there is a pair of processes running from the inner hexagon towards the figures, twelve in all. 

 Four of these join up with the figures, but the rest stop short. Here there is a little discrepancy ; 



