Snoiv Crystals. 279 



bona, either sun-dried or in the shape of bone-ash, are imported 

 from South America into England. 



Bone-ash is bone burnt in contact ivith the air until its 

 organic matter is destroyed ; it yields a quantity of bone phos- 

 phate equivalent to 70 or 90 per cent, of ordinary phosphate of 

 lime, according to its degree of purity. When burnt without 

 contact of air, animal charcoal is obtained ; this is used to clarify 

 sugar, juice, etc., and when spent is burnt over again. After 

 being thus burnt twice or thrice, it becomes comparatively use- 

 less to the sugar-refiners, and is sold to manufacturers of super- 

 phosphate. According to a number of analysis made of this 

 substance in my laboratory, it may be said to average from 70 to 

 80 per cent, of phosphate of lime. 



Such, then, are the substances which furnish our agricul- 

 turists, our lucifer-match manufacturers, our colour-makers, 

 etc., with their supplies of phosphate of lime. It is needless, 

 perhaps, to add that agriculture absorbs by far the greatest 

 portion of this phosphate, and we may be thankful that there 

 exists so plentiful a supply of it. In a future paper I will con- 

 sider our present sources of ammonia. 



SNOW CRYSTALS. 



BY E. J. LOWE, ESQ., E.E.A.S., ETC. 



When we observe the snow beating against our windows, or 

 being drifted into heaps by the wind, we regard it with interest, 

 we admire its dazzling whiteness, and we are thankful to look 

 upon its carpet, because it is a protection to tender plants from 

 the injuries of severe frost. Few of us, however, are aware of 

 the exquisite beauty of some of these snow crystals; very 

 various in form, and sometimes exceedingly intricate, it be- 

 comes impossible to do justice to a snow-storm. The difficul- 

 ties to be overcome are great : a lovely star descends and 

 alights upon a leaf; paper and pencil are at hand, and the mag- 

 nifying-glass reveals its beauties, but before it can be sketched 

 in all probability it has melted and gone. If snow falls in 

 showers, and the temperature of the air is above the freezing- 

 point, it is almost impossible to sketch the crystals. Once or 

 twice a year the weather is sometimes favourable for these 

 investigations, and such a day was February 10, 1864. Let us 

 take this day as an example : — 



There had been a severe frost, the temperature falling to 

 15'8 at the height of four feet, and to 13"1° on the grass. The 

 morning was overcast, foggy, dark, and having a peculiar yellow 



