620 Extracts from the Minute Book of the Geological Society. 
The colour of the limestone is various, though the prevailing one 
is light-blue, or grey, changing at times to dark-blue or nearly 
black, these again being marbled with infinitely various tints of red 
and other colours. This variety of colours, and the high polish 
which the stone is capable of receiving from its hard and close- 
grained texture, render it an article of some importance as a marble 
for the manufactory of slabs and chimney-pieces. The foot pave- 
ments also in the three towns of Plymouth, Stonehouse, and Dock, 
and their environs, are almost all formed of blocks from the lime- 
stone quarries, and it is in these pavements, after a shower of rain, 
that the beauty of our marble may best be observed. 
Until within a recent period, it was a question whether the 
limestone of Plymouth contained any animal remains : the ac- 
count of my having discovered these bodies in our rocks has been 
inserted in the 4th volume of the Society’s Transactions. The 
accuracy of my former statements, however, having been called in 
question, I can now affirm that the proofs of the presence of organic 
remains in our limestone, are abundant and indisputable ; and so 
generally indeed do these remains pervade almost every part of our 
limestone, that I can only wonder that they have remained so long 
unnoticed. Visible traces of them meet us at every step, and there 
is hardly a hill or quarry where they do not obtrude themselves to 
the view of the curious. They consist of madrepores, tubipores, 
millepores, corals, entrochi, and various univalve and bivalve 
shells, among which are the anomia terebratula, and producta. 
The madrepores are not confined to any particular stratum in 
our limestone, but are discoverable in almost every part of it, 
although they are variable in their quantity, being sometimes not 
very distinctly visible, and at other times occurring in extensive 
masses or layers. The other animal remains are not diffused so 
