ON SIMILARITY OF FORM IN SNOW CRYSTALS. 201 



On the Similarity of Form observed in Snow Crystals as 

 compared ivith those of Camphor under certain conditions of 

 Crystallization. By Joseph Spencer, Esq. (Read before 

 the Greenwich Natural History Club, Jan. 2, 1856.) 



Investigations tending to throw some light on the laws 

 which determine the external forms and internal structure 

 of crystallized bodies, may not be considered devoid of in- 

 terest. The field of research is so extensive, the forms of 

 crystals so varied and beautiful, and a knowledge of their 

 primitive and resulting forms of such importance to the 

 kindred science of chemistry, that any additional facts on the 

 subject may be considered desirable. Much attention has 

 been given of late to the peculiar forms assumed by snow, or 

 to speak more correctly, by water under certain conditions of 

 crystallization. The subject was first introduced, I believe, 

 by a distinguished member of this Society, and has since been 

 most ably worked out by liim. Every one must have been struck 

 with the beauty and variety of snow crystals, and some very 

 truthful delineations of them have been published. A great 

 difficulty sometimes has been felt by those desirous of studying 

 them from their very perishable nature, as they require to be 

 maintained at a temperature below the melting point of ice, 

 or 32 degrees of Fahrenlieit's thermometer. The usual plan 

 of viewing them has been by the microscope in the open air, 

 or at a window. Having tried both plans, and found them 

 beyond my powers of endurance for any length of time, I 

 have been driven to devise a plan for viewing them within 

 doors, and in comparatively warm rooms This plan I shall 

 be happy to explain, at the conclusion of this paper, to any 

 members of this Society who may be interested in the sub- 

 ject. Very considerable interest attaches to the forms 

 assumed by snow, from the intimate connexion that appears 

 to exist between the production of certain forms of crystal- 

 lization, and certain states of the atmosphere. Meteorology 

 has of late years obtained that attention which its importance 

 deserves, as only by a slow and laborious collection of facts, 

 extending over a series of years, can we hope to arrive at a 

 knowledge of the laws which control the mighty agencies at 

 work in the atmosphere of our earth, and the study of which 

 is of such importance to the health and well-being of man. 

 It would be very desirable, however, in the study of snow- 

 crystals, to find some substance similar in its habits of 

 crystallization but of a less perishable nature, and which 

 would enable us to trace the progress of the crvstals from the 

 simplest up to the most complicated forms ; so that reasoning 



