2 
generally, as illustrated by the existing vegetation of the 
globe, as well as at some of the principal coal-fields of this 
country, more especially the Lancashire, Newcastle and Dur- 
ham, and Colebrook Dale, to see whether any, and what, 
similarity existed between these and the Yorkshire ; and 
also, if any between them and the coal-fields of distant lands. 
For as the quality of coals from different districts varies 
considerably, we should be prepared to expect a slight 
diversity in the plants that have contributed to the forma- 
tion of each ; which is actually the case to a limited extent, 
as may be seen by comparing in a superficial manner the 
number of species of plants found in each of the above- 
mentioned coal-fields, all of which are supposed to be frag- 
ments only of one continuous series — the great northern coal- 
field. Upon this subject I shall not venture an opinion, 
it being no part of my object to prove the identity of these 
three great deposits, but rather to endeavour to show that 
there is not only a slight diversity in the fossils of each 
locality, but also in the individual seams of one coal-field ; 
for upon no other grounds, it has long appeared to 
me, could we account for the very different quality of 
the coals worked at Barnsley, Lofthouse, Rothwell Haigh, 
Manston, Churwell, Middleton, and Halifax, in this district ; 
as also in certain seams of superior quality which occur in 
the Lancashire and Newcastle coal measures. And reason- 
ing from analogy, as we know that sugar, gum, and starch, 
though apparently so different in qualities and properties, 
are all primarily derived from the same elementary consti- 
tuents, under slightly different proportions or arrangements ; 
and as we also know that plants yielding such an innumerable 
diversity of substances in their recent state, are yet all 
resolvable into carbon, oxygen, hydrogen, and nitrogen, 
why may not coals primarily derived from vegetable reliquiae, 
yet possess varied degrees of inflammability, &c, from the 
