177 
to change from pure clay to sandstone, being present only in 
the clay ? thus showing the action of a current of water 
during their deposition : whether the large sigillarise and 
calamites and lepidodendrons are filled up with the same sub- 
stance as the adjoining stratum? In fact, the inquiries to be 
answered by a complete collection of the fossil vegetables 
accompanying the coal measures, are so many, so varied, 
so highly interesting and important, that an extended enu- 
meration of them would far exceed the limits of this paper. 
When, therefore, the members of the Society have 
placed in the hands of the Council a large collection of 
Yorkshire fossils, the Council will be able to procure similar 
specimens from other coal fields, by exchanging with 
other local Museums any duplicates that we may possess ; 
and thus we shall not only be able to learn the Geological 
phenomena of other districts, but have the means of 
adding to the interest, and enhancing the value of our 
own Museum. But I would not stop even here ; I 
would endeavour to obtain a complete suite of fossils both 
from the strata above and below the coal measures. It is 
well known that if we had anything to offer in exchange for 
fossils from the Silurian system, the Lias or the Chalk, we 
should soon have a very respectable collection of these fossils, 
for in many Museums in the south of England, where these 
fossils are collected to a considerable extent, they have few, if 
any, coal fossils ; indeed, the specimens they do possess are 
generally of no practical utility, as in many instances their 
locality is not known ; they woidd be very glad therefore to 
make an exchange with us, which would cost neither party 
any thing, but would greatly benefit both. 
Being placed in this position, we could satisfactorily say 
whether the organic contents of this coal field are the same 
as those of Lancashire, or whether they were more similar 
to those of Staffordshire, or of Northumberland, or Durham? 
3 
