1868. | Chemistry. 233 
cussion which followed its delivery, could hardly be given in the 
small space we can devote to the matter; and we shall only say 
that Mr. Forbes considers that a combination of the Plutonic and 
Neptunian theories will best account for the results developed by 
modern research. He showed that silica occurred in nature as an 
igneous product in recent lavas ; that it occurred also as an aqueous 
product in different forms deposited from solution ; and also as a 
gasolytic product in tubes from the decomposition of fluoride of 
silicon. As regards the origin of granites, while he is satisfied 
that many of the so-called granites and gneisses are really sedi- 
mentary products of the breaking-up of true igneous rocks by 
aqueous agency, and subsequently reconsolidation, he also believes 
that true igneous and eruptive granites do exist, and he replied at 
some length to the arguments of those who dispute altogether the 
igneous origin of these rocks. Assuming that the whole of the 
constituents of this earth were once in a state of vapour, he con- 
siders that these vapours obeyed the law of gravity and arranged 
themselves in zones according to their densities. He thus con- 
cludes that the central nucleus of the earth must contain an 
accumulation of the denser metals and their compounds, an hypo- 
thesis which is supported by the fact, that while the mean density 
of the earth is about 5:4, the density of the exterior crust is only 
2:75. At the moment of solidification the earth must have formed 
a true sphere; but the outer crust becoming subject to volcanic and 
other forces, the surface would be soon broken up into mountains 
and valleys, and subsequent aqueous action would produce other 
changes in the first-formed rocks. Metamorphic action, promoted 
by heat, pressure, chemical action, aqueous or gasolytic agency, or 
altogether combined, would continue to go on, and produce that 
state of our earth which offers itself for the study of the modern 
geologist. ‘The discourse, of which the foregomg is the merest 
outline, was followed by a discussion, in which Sir R. Murchison 
and Professors M‘Donald and Morris took part. For an excellent 
report of this we may refer the reader interested in the matter to 
the ‘Chemical News’ for February 28. 
The last meeting of the Society which we can notice was held 
on March 5. On that evening Professor Wanklyn gave the sub- 
stance of a paper ‘‘ On the Action of Oxidizing Agents on Organic 
Compounds in the presence of an excess of Alkali—Part 1. Am- 
monia evolved by Alkaline Permanganate, acting on Organic Nitro- 
compounds.” 
The paper related to the author’s process, before referred to, for 
determining the amount of nitrogenized organic matters in waters ; 
and he gave a list, first, of the substances which he found to yield 
all, or very nearly all, their nitrogen in the form of ammonia, when 
distilled with permanganate of potash in the presence of free alkali. 
Among these were amylamine, diamylamine, asparagine, hippuric 
