THE SILURIAN ROCKS OF THE EASTERN MENDIPS. 
81 
glomerate to the Silurian rocks exposed by the rails at 93. 
Unfortunately, the farmer who has already had 17 trenches dug 
in his fields, objects to having any more made. 
Section in the eastern wall of the Downhead Quarry, Mendips. 
Length of section about 10 yards. 
(The numbers correspond to those in the text, page 81). 
2. — Downhead. 
The Downhead quarry has been considerably enlarged during 
the last few years, and at the present time (1912) is being rapidly 
extended to the north, leaving an upstanding mass of rock in 
the middle of the quarry. This upstanding mass is of particular 
interest, as it is to a considerable extent composed of tuff inter- 
bedded with the andesite. The best section is seen in the cutting 
between the eastern wall of the quarry and this upstanding mass, 
and is as follows, at the top : — 
5. Pyroxene-andesite, often much crushed, extending to 
the southern margin of the quarry. Thickness 100 feet or more. 
4. A band of fine tuff showing marked spheroidal weather- 
ing. This band is better seen in the middle of the 
quarry, where the unweathered portions form prom- 
inent bomb-like masses. The weathered portion ft. ins. 
crumbles readily into little polygonal pieces ... 1 6 
3. A band consisting of rounded masses of andesite 
with slickensided surfaces embedded in crushed and 
weathered andesitic material, much of it reduced to 
the appearance of crushed red shale ... ... ... 80 
2. Fine-grained purple or reddish tuff dipping at about 
6o° S. or a little E. of S.... ... ... ... ... 70 
1. Pyroxene-andesite considerably crushed and slicken- 
sided to end of quarry. Thickness not ascertained. 
These bands are somewhat impersistent, thus while band 4 is 
(1912) finely exposed on the southern face of the upstanding mass 
