86 PROCEEDINGS COTTESWOLD CLUB 1903 
(3) Coral muds and sands, deposits of which accumulate 
round coral reefs; (4) Various kinds of muds, sands and 
volcanic and chemical products, the latter formed zz set 
on the floor of the ocean. I have only mentioned the 
chief deposits now taking place, and refrained from details, 
only noticing the main characters. The point which I 
desire to bring out is that the deposits now taking place 
are but repetitions of what has been going on from the 
earliest times of which we have knowledge of the stratified 
rocks. 
One of the oldest sandstone rocks may be studied 
within our own area: it is that of the Holly Bush sand- 
stone, exposed on Raggedstone Hill, near Eastnor. A 
microscopic examination shows that it is made up of 
mineral grains derived from the denudation of still 
older rocks, including at least some of igneous origin. 
There are also other sandstone formations in our own 
district, among which may be mentioned the Old and 
New Red Sandstones and Millstone Grit. The latter 
formation underlies the Coal Measures and may be studied 
within the Bristol and the Forest of Dean coalfield. It is 
impossible for me, in this address, to describe all these 
sandstones, and I will therefore select one, that of the 
Millstone Grit, which is instructive because of the litho- 
logical difference of this rock in the Bristol and South 
Wales basins from the contemporaneous formation in the 
Forest of Dean. 
In the Bristol area the analysis of five samples of the 
rock shows it to contain an average of 97°75 per cent. of 
silica, the remaining 2°25 representing small quantities of 
iron, lime, &c. Examined under the miscroscope it shows 
that the silica is derived from small grains of quartz, but 
these are so closely cemented together that sometimes it 
is difficult to clearly define the outlines. Owing to this 
compactness the Millstone Grit in the Bristol area is 
