ON SIMILARITY OF FORM IN SNOW CRYSTALS. 203 



for themselves the crystals of snow and of camphor, and of 

 throwing still further light on the subject. 



Further Observations on the Similarity of Forms observed 

 between Snow Crystals and those of Camphor. By James 

 Glaisher, Esq., F.R.S. (Read before the Greenwich 

 Natural History Club, Feb. 6, 1856.) Plate XII. 



The field of inquiry thus opened by Mr. Spencer has since 

 engaged a portion of my attention. The following are some 

 of the results of observation carried on at intervals, the solu- 

 tion being provided by Mr. Spencer, and a part, I believe, of 

 that employed by him in his own experiments. The follow- 

 ing are my notes on the subject. 



The process of crystallization, according to my own observ- 

 ation, appears to proceed rapidly, and to commence simul- 

 taneously with the action of the air upon the liquid ; but to be 

 by no means certain of proceeding similarly under apparently 

 similar conditions. 



The process of crystallization, in this case, bearing the closest 

 analogy to that of snow, and the one of most frequent occur- 

 rence, presents an endless succession of minute, round, moving 

 dots, passing to and fro with the restless movement of animal- 

 cules ; every instant these globules very perceptibly increase in 

 size, and soon develop points, generally six in number, which 

 continue to enlarge until they assume the character of 

 arborescent pinnae, the additions to the elementary figure 

 being effected at an angle of (50^. The crystal, when arrived 

 at perfection, immediately begins to simplify, and continues 

 to do so until quite evaporated. If, however, the room be 

 cool, and the evaporation proceed slowly, as is best in these 

 experiments, it is not unusual to perceive one or two of the 

 radial arms elongating themselves at the expense of the rest, 

 and the greater number subsiding into a kind of crystalline 

 film or disc, of which I will speak presently. 



These figures never appear to attain to any great degree of 

 complexity, or to be other than arborescent when in their final 

 and most perfect stage of development. In some of the 

 richer specimens may be seen, around the nucleus, a somewhat 

 thick aggregation of little drops or knobs ; but these are not 

 arranged with the geometrical precision to be observed in the 

 crystals of snow, and speedily disperse into the crystalline 

 matter of the arms, to which they contribute a still more 

 arborescent character. The downward and tertiary spike, 

 common to the snow crystal, is here often met with, and forms 

 a point of analogy worthy of remark. 



