12 
factor in rock making? If they examined the water of ponds 
at certain periods of the year minute specks might be observed 
in a state of activity, generally with a more or less jerking 
motion. Placed under a microscope these specks would be 
seen to be living organisms, with a body more or less jointed, 
and mostly protected with a semi-calcareous or horny shell. 
The objects before them, from the Limestone of Clifton, were 
related to these recent Entomostraca, but were marine or 
brackish water forms. In early Carboniferous days these 
creatures must have swarmed in the waters, and their shells 
contributed largely to the building up of the rock masses. 
Taking another microscopic section of the Limestone, it was 
found to be mainly made up of the remains of Encrinites. In 
the Carboniferous seas the Crinoids lived in vast numbers, as 
shown by the abundance of their remains in the Limestone. 
The Black Rock at Clifton is largely made up of the remains 
of Encrinites. Several microscopic photographs were thrown 
upon the screen, in which the characteristic net-work structure 
of the joints was well shown. One of the chief Limestone- 
forming creatures of the Carboniferous period were the Corals. 
An actual Coral-reef of that period is to be seen now near 
the entrance to the Suspension Bridge, on the Clifton side, 
sections of which, showing the structure, were thrown on the 
screen. Mr Wernerep then explained the growth of Coral- 
reefs in modern seas, and pointed out how that in the present 
day the Coral insects are building up Limestone rocks. These 
are constantly undergoing destruction ; the sea-waves dashing 
against the reefs break off portions, which are soon reduced 
to minute fragments—these form beaches of coral sand. Then 
again the sea dissolves the lime, but this is re-deposited in a 
curious way; it becomes aggregated around particles of sand 
or of other minute organisms, and assumes the form which is 
known as Oolitic. ‘Let them now return to the Clifton rock, 
and they would find some beds formed entirely with the Oolitic 
structure. Microscopic sections of this rock were exhibited, 
and Mr Weruerep pointed out that in the centre of each 
granule there was a nucleus, around which lime had been 
