402 
tion almost entirely into the type of organic form. The edges of 
the rays were marked with pinnate serrations or strise. 
In this last form we are strongly reminded of the beautiful stel- 
late figures, like six-petalled flowers, which have been recently 
described by Professor Tyndal as being developed within a block 
of ice, when the rays of the sun are concentrated on a point in 
the interior of it by a burning lens. 
Besides the forms now described, the snow which fell on the 26th 
contained many others, any one of which would well repay the trouble 
of drawing, though no figure can give an adequate idea of the ele- 
gance of the actual object, in which the most beautifully symmetrical 
flowers, and elaborately divided fern leaves, are repeated with that 
marvellous fidelity with which inorganic nature occasionally imitates 
the forms of organisation when the formative forces are directed by 
an undeviating symmetry. 
But the ordinary snow of our latitude is not thus constituted. 
We may seek in vain in the snow as it usually falls with us for the 
beautiful stellate crystalline groups now described. Why is this ? 
There are doubtless needed, for the perfect development of the ice 
crystals in the freezing cloud which is about to descend in the form 
of snow, several conditions, as yet but partially understood. Of 
these, it is posssible that a temperature considerably below the 
freezing point may be one, and a stillness in the higher regions of 
the atmosphere, where the snow is formed, another. It is exceed- 
ingly probable, as has been ingeniously suggested by Fr. Vogel,* in 
explanation of the phenomena of hail, that if the atmosphere be 
perfectly still, the particles of visible vapour constituting the cloud 
may be cooled far below the freezing point without freezing ; and if 
in this state a crystal of ice be precipitated into the cloud from some 
higher elevation, or the stratum of cold vapour be agitated by 
sudden exposure to some atmospheric current, the balance between 
the forces of cohesion and adhesion will be destroyed, and the whole 
cloud will instantly shoot into beautiful ice-crystals, and will fall 
towards the earth as stellate snow ; for the peculiar constitution of 
the visible vapour is such, that unimpeded action will be permitted to 
the forces of crystallisation, and no mechanical obstacle will be offered 
to the perfectly symmetrical development of the crystalline groups. 
* See Muller’s Kosmische Physik, p. 421. 
