199 Mr. Brayktf oH the liationak of the Formation [SEPt. 



the general fact, in addition, that in all cases completely within 

 our sphere of observation, the solid results from the liquid state, 

 may we not fairly infer, that the liquid state invariably takes 

 place between the aeriform and the solid? — that it is a necessary 

 and inevitable step in the production of solid from gaseous 

 matter? 



I now proceed to adduce some experimental evidence on this 

 point. In the subhmation of bodies which do not require a very 

 elevated temperature for their volatilization, and which are, 

 therefore, fully open to observation during the process, such as 

 benzoic acid, some of the salts of ammonia, and sulphur, we may 

 observe fhe following facts. If the temperature of the vessel or 

 portion of the vessel into which the vapour rises, is insufficient to 

 retain the substance, for a sensible interval, in the liquid state, 

 the result is an indistinctly fibrous or a compact mass, bearing, 

 however, marks of fusion. But if the heat is sufficient to allow 

 the condensed vapour to remain liquid a sensible portion of 

 time, more or less perfect, though usually minute crystallization 

 is the result. The former of these cases appears to me to be 

 precisely similar to that of the production of the filamentous and 

 the mamillary carbon. And as an instance in nature of a corre- 

 sponding kind, I may refer to the various forms of volcanic 

 sulphur, when viewed in connexion with the chemical and geo^ 

 logical circumstances under which they are produced. 



The evidence which I have given, tending to show that 

 the liquid state always intervenes between the solid and the 

 aeriform, also induces me to believe, that in the transfer of car- 

 bon from the negative to the positive pole of the Deflagrator, 

 observed by Dr. Hare,* the carbon is first liquefied, and then 

 evaporated, being driven in vapour to the opposite pole by the 

 galvanic current. This is the converse of the deposition of 

 carbon bearing marks of fusion : in that case the temperature is 

 insufficient to preserve the carbon in a liquid form ; in this, it is 

 too high to allow that form to be retained, the substance imme- 

 diately acquiring elastic fluidity. 



It may be useful to add a few words in explanation of the 

 various forms assumed by the deposited carbon. I have already 

 suggested an idea on the origin of the capillary form ; and f 

 may here remark, in continuation, that though for various 

 reasons already stated, we must not regard crystallization as 

 having been, in any material degree, concerned in its produc- 

 tion, yet a species of polarity, as Dr. Colquhoun has already 

 observed, has undoubtedly had an influence in its formation ; 

 and it appears to me, that the tendency to a rectilinear direction, 

 which so many of the most refined investigations of modern 

 science have shown both ponderable and imponderable matter 

 to possess, or the tendency to polarization^ is prior, in its agency 

 • See AmaU^ N. iS. vol iv, p. 121. 



