202 On a Case of Formation of Ice on an Alkaline Solution. 



exactly the same figure and the same dimensions. Every one of 

 them consisted of a wheel, or star, with six equal rays, bounded 

 by circumferences of equal diameters; having all the same num- 

 ber of rays branching from a common centre. The size of each 

 of those little stars was equal to the circJe presented by tlie secr 

 tion of a pea into two equal parts. This appearance continued 

 during three hours, in which time no other snow fell; and as ther^ 

 was sufficient leisure to examine them with the strictest attention, 

 we made the representation given in fig. 1. 



" Water in its crystallization seems to consist of radii diver- 

 ging from a common centre, by observing the usual appearances on 

 the surface of ice : — perhaps therefore it may be possible to ob- 

 tain the theory and to ascertain the laws from which this structure 

 results. , 



" Monge, President of the National Institute of Paris, no- 

 ticed in failing snow, stars with six equal rays descending, during 

 winter, when the atmosphere was calm. Uaily records this in his 

 observations on the muriate of ammonia." 



As all regular crystallization must be governed by, and depend 

 on, some imalterable laws in nature, 1 have no doubt but the 

 Russian snow observed by Dr. Clarke, and the Parisian stars no- 

 ticefdby M. Monge, and the above radiations on this alkaline so- 

 lution, were identically from the same cause — the presence of am- 

 monia, and nitre, in both. The quantity of ammonia produced in 

 large cities must he immense: Independent of every other source, 

 what must be formed in the ordinary culinary operations of the 

 kitchen ? this must be driven into the atmosphere. From the same 

 source nitrogen per se may be supplied in no mean quantity, or 

 liberated by the decomposition of a portion of the ammonia. 

 May not condensation be of use in atmospherical combinations, 

 and nitrates as well as ammoniacal salts formed, and the aqueous 

 vapours impregnated with these saline productions, prior to freez- 

 ing or forming into snow, and the beautiful regularity of this phae- 

 nomenon proceed from the habitudes of ammoniacal crystalliza- 

 tion as recorded by Hauy P May not this also account for the ex- 

 traordinary quantity of nitre found in some soils where deep ve- 

 getable mould predominates? The nitrogen descending with rain 

 or snow, may combine with the potash of decayed vegetables al- 

 ready existing in the soil, and become the parent of this native salt. 

 Or can it be possible that the mere abstraction of caloric has any 

 share in the formation of potash, and hence nitre ? It is well 

 known that frost alone produces in potatoes a saccharine matter 

 that renders them sensibly sweet to the taste. It is also known 

 to you, that potatoes once gone into putrefaction by the effects 

 of frost, contain nitre in such quantity as to answer the purpose 

 of making match' paper : before the potatoe undergoes these 



changes 



