375 
of Edinburgh, Session 1864-65. 
II. Origin of the Coal. — In different localities, and under differ- 
ent circumstances, it has at one time, apparently, consisted of drift 
wood and leaves ; of peat bog, marsh, littoral or forest vegetation 
submerged in situ and subsequently re-elevated ; or of marine\ege- 
tation (kelp) subsequently elevated. It has been found mainly in 
ancient lakes, estuaries, bays, fjords, coasts, or seas. Its associated 
strata present frequently, if not usually, alternations of marine 
(shell and kelp beds) with terrestrial deposits (dicotyledonous leaf 
or fern beds) ; indicating the occurrence of repeated and irregular 
oscillations of the relative levels of land and water during their 
deposition. 
III. Stratigrapliical Relations. — The best class of coals is refer- 
able to the Lower or older group of the Tertiary system ; belonging, 
however, to different ages in this group. 
Lignites, jet, and fossilised wood occur also in all the newer or 
superjacent Tertiaries, as well as the post-tertiary strata ; while drift 
ivood and submerged forests may be seen in process of fossilisation 
at the present day. 
Not unfrequently the coal-beds rest immediately on the funda- 
mental rock of the country, which is usually metamorpbic slate, 
(probably of Silurian age), though sometimes granite. 
The coal strata are frequently disturbed by eruptive or intrusive 
Trappean rocks of Newer Tertiary age, which sometimes tilt them up 
vertically, or throw them completely over. They are pierced like- 
wise by Trap-dyhes, and characterised by faults or dislocations re- 
sembling — save, perhaps, as to the scale on which they occur, — 
those of our own Paleozoic coal-measures. These Traps sometimes 
coke or cinder the immediately adjacent coal ; more frequently, 
perhaps, the lithological character of the latter is unaffected. 
TV. Associated Strata — 
a. Conglomerates (locally known as “gravels” or “ce- 
ments”), usually coarse and quartzose ; frequently of 
a plum-pudding stone character ; generally ferruginous ; 
passing into 
h. Grits, which again graduate into sandstones. Some of 
the latter are sufficiently hard and pure to be useful 
