651 
of Edinburgh, Session 1865-66. 
unchanged, though the wood is exceedingly reduced in compact- 
ness. Nor even with the aid of pressure can we do more than 
increase the density; we bring their particles nearer together, but 
we do not affect the character of the particles themselves ; if pres- 
sure could perform this, why should it not have Ibeen equally 
effective for the induration of clays or other soft hydrous minerals, 
which in certain states bear considerable resemblance to lignite, 
many of these having been subjected to pressure as great, or even 
far greater ? 
It is to a reconstruction of the residue from decomposition into 
new, more insoluble, and more permanent combination, that any 
great physical differences should be due, and to this only; this 
cannot, however, be effected while the particles of the solid vege- 
table matters are unable to move to each other’s affinities while 
their position is fixed by cohesion ; they must be brought into 
renewed chemical contact before they can enter into those com- 
binations which give to coal qualities we have to account for. 
If now we seek the assistance of an elevation of temperature 
sufficimit to fuse or volatilize portions of the coal, so as to gain in 
this renewed chemical contact, so necessary for recomposition, we 
shall find that, although we may effect this, the results are not 
altogether of the kind we want. 
Suppose we attempt to go no further than partial fusion, although 
we should certainly indurate its particles considerably, and give 
them some degree of lustre, and also effect favourable recomposition 
in the substance in regard to its chemical composition, we should 
certainly obliterate that laminated appearance coal often presents, 
and render the whole perfectly homogeneous, both in its physical 
character and chemical composition ; and we should further most 
likely destroy the distinctions of those boundaries which separate 
the coal-seam from above or below, and also change their uniformity 
of direction. But, in all probability, in attempting the fusion only, 
we could not avoid decomposing a portion of the coal into gas, and 
this being mechanically retained by the semifluid mass, would render 
it porous throughout ; and thus, although we might gain consider- 
ably in some of the properties of coal, such as those of hardness, 
lustre, coherence, we should lose in compactness — the vesicular 
appearance such a product would present would neutralise all we 
