202 NOTICES OF THE MEETINGS [May 21, 
chemical reactions. This difference is expressed by assuming that 
the hydro-carbon is differently distributed in the two substances. 
Looking at the above formule, it will be perceived that the con- 
version of the one substance into the other would be effected by the 
transference of hydro-carbon from one to the other part of the 
system. The change in this case has not yet been effected ; but in 
certain other instances we are enabled to effect very analogous 
transformations, and to recombine the particles in the interior, as it 
were, of the body itself. 
One or two instances were shown of this isomeric metamorphosis, 
which were so selected as to illustrate the modes by which it could 
be effected. For example—styrol, (an oil procured by the dis- 
tillation with water of the liquid storax), by the application of heat, 
is converted without either the addition or the loss of any chemical 
substance into a transparent solid, in its ultimate constitution 
identical with the oil. The formula of the oil is C, H,, that of the 
solid according to Blyth and Hofmann, who first made it a subject 
of investigation, C, H,. 
In certain cases these changes may be brought about by a chemical 
action very analogous to that of fermentation, by which sugar is 
converted without alteration of weight into carbonic acid and 
alcohol. There is a body called aldehyde, C, H, O, a very volatile 
substance boiling almost with the warmth of the hand, and the 
vapour of which is about 14 times as heavy as air. By the addition 
of one drop of sulphuric acid it is converted into a body which boils 
at a higher temperature than water, and the vapour of which is 43 
times as heavy as air. Our knowledge is too imperfect to state the 
precise mode in which the elements are re-arranged, but from the 
density of the vapour we infer that the molecule of the transformed 
aldehyde contains three times the number of atoms of the original 
body and is C, H,, O,. Oil of turpentine is in a most remarkable 
degree susceptible of these metamorphoses. By the action of sul- 
phuric acid it is converted into oils, isomeric with it, but each 
differing from it in some one or more properties. Great heat is 
evolved during the change, due doubtless to the chemical combi- 
nation which is taking place. In certain cases, as, for example, 
the formation of paracyanogen by the decomposition of cyanide of 
silver, this heat is so great as to cause the vivid ignition of the 
substance. 
Acquaintance with these facts is necessary to view in their 
scientific connexion certain phenomena of the elemental bodies 
which go under the name of allotropy, and which are to them, 
precisely what isomeric phenomena are to compound substances. 
This allotropy has been observed in the case of many elements, 
carbon, boron, silicon, selenium, sulphur, phosphorus, arsenic, 
and possibly oxygen—from these sulphur and phosphorus were 
selected as presenting points of peculiar interest. 
At a few degrees above the boiling point of water, Sulphur 
