Side- Light upon Coal Formation. — Gresley. 71 
•garnet-red and yellowish plays of color which I have repeatedly 
observed upon or in the knife-edges of very thin splinters or 
flakes of coal, testify to the presence in it of this resinous ma- 
terial. Fragments of woody-looking and more succulent tissues 
of some of the better preserved black laminae evidently have 
their cells and tubulous parts filled with solidified liquid hydro- 
carbons — the amber-like material. Clearly also, this material 
is to a large extent the cementing matrix or groundmass of the 
coal. To it, it seems to me, coal chiefly owes its body, solidity 
or its cohesive strength. It is this same substance, I claim, 
that gives to coal its somewhat loose or open texture (texture 
revealed by visible vegetable filaments, fragments and off- 
shoots), notwithstanding its frequent close approach to homo- 
genity in mass. In other words, the more undecomposed 
parts of plants in coal seem to have become not only impreg- 
nated by this liquid amber-like substance, but embedded in 
or surrounded by it in a manner somewhat analogous to coral- 
fragments, shells, etc., in the calcareous matrix of marble. 
Now, this mineral resin is doubtless what one or two fanciful 
observers have mistaken for plutonic, or volcanic, oil, which 
they supposed flowed from rents in the earth and collected 
in pools or basins, saturating the vegetable debris or produc- 
ing impressions of bark, leaves, etc., on solidification. Other 
writers seem to be pretty sure that in this resin-like product 
they can detect the action of bacteria and fermentative pro- 
cesses upon microscopic algae. 
But whatever this substance or compound is, it is an ele- 
ment in coal-bed formation that plays a very important rule. 
That it is not confined to scams of coal is proved by its occur- 
rence in many of those perplexing pitch-coal, meandering, 
streaky, and vein-like forms (of endless variety of shapes and 
sizes) very commonly seen in the shales, fire clays, sandy beds, 
and bony layers associated with beds of coal, and many of 
which actvially proceed from or are clearly traceable right into 
the coal-bed. The physical, stratigraphical as well as chemical 
composition of these pitch-coal forms not in the seam, so 
closely agree with coaly forms of similar aspect m the seams 
that here is practical evidence that whatever these coaly forms 
represent or were originally, they are one and the same thing 
or things. Moreover, where suitable specimens of both have 
