653 
of Edinburgh, Session 1865 - 66 . 
is not owing to any superior heat applied for the production of the 
more carbonaceous substance ; for how, indeed, could superior heat 
be applied to these parts alone? Why, therefore, should not the 
bituminous coal be itself produced from brown coal without the 
aid of any increase of temperature over that which has obtained 
in its formation ? there being no greater chemical difference between 
these than there is found to be between the bituminous coal and 
the fibrous anthracite. 
But, besides the internal evidence afforded by coal itself that 
substances very rich in carbon can be eliminated at low tempera- 
tures, we have the authority of Bischoff for asserting, that for the 
elimination of a substance still further removed from organic 
matter (graphite) high temperatures are not necessary. 
On the whole, it would therefore appear there is indeed no 
absolute necessity to provide any considerable elevation of tempera- 
ture to bring about the chemical change required to convert decom- 
posed organic matter into substances resembling anthracite; and 
further, it would also appear that hardness gained in such a manner 
would render the product porous, or, if these pores were subsequently 
filled, the anthracite would appear amygdaloidal. 
Thus we have to rely upon the solvent powders of water as the 
only means by which recomposition can be effected, — as the only 
agency which can modify these vegetable substances in the manner 
we would wish, and which not only favours their decomposition, 
but allows of their recomposition and deposit as a hard, compact, 
coherent, and lustrous mineral. 
In conclusion, I have to apologise for the incompleteness of these 
investigations ; nothing but my inability to prosecute further 
researches for some time, owing to the removal of the laboratory 
to a distant part of the colony, and the consequent suspense of 
analytical operations, induces me to forward them in this state. 
There was one part of the subject, especially, I w^as very anxious 
to examine further — that treating upon substitution — for it was 
apparent, if it could be ascertained whether or no gases are able to 
substitute each other, some further light would be shown upon the 
manner in which these absorptions are effected, since, in the absence 
of solvents, there would be fewer chemical affinities to interfere. 
