192 PROCEEDINGS COTTESWOLD CLUB 1920 
They are all of them very largely composed of quartz fragments, 
contain felspar fragments sparsely scattered about, and most 
of them contain numerous fragments of igneous rocks. The 
last are generally angular, though in one slide they show 
rounding. They can all be classed as ashy quartz grits. The 
igneous fragments are generally of an andesitic nature, some 
may be felsitic and some are of a black opaque substance 
enclosing felspars. 
The andesitic fragments often show small porphyritic 
plagioclase felspars in a ground mass of small felspar needles 
which may or may not show flow structure, occasionally the 
porphyritic felspars are absent. Amygdules sometimes occur. 
The Llandovery Sandstone exposed by the road to the west 
of the Huntley Quarry shows in sections numerous quartz 
grains, usually well rounded, but sometimes angular, amongst 
which are to be seen grains of igneous rocks, probably felsites, 
much decomposed. One shows a grain of a coarse felspathic 
quartz grit or ash, a grain of a fine grit, some rounded grains 
of plagioclase felspar and a well-rounded fragment of a fresh 
vesicular andesite or felsite. 
Thus microscopic investigation bears out the result of the 
examination of hand specimens, and leads one to the conclusion 
that there is in general not very much difference between the 
two sets of rocks. The chief differences are that the typical 
Llandovery Sandstone has its components more rounded and 
that the Huntley Quarry rocks contain igneous fragments of a 
more distinctly andesitic nature as well as fragments of a rock 
which Dr. Callaway regarded as a partly decomposed dolerite. 
The next argument that Dr. Callaway advances, namely 
that the type of ashy rock seen in the Huntley Quarry is not 
to be regarded as Silurian because it is one unknown in the 
Midland Silurians, is one that now needs modification. Professor 
Lloyd Morgan and Professor Reynolds have, since Dr. Callaway 
wrote, found Ashy Silurians of Llandovery or Wenlock age at 
Tortworth, 1 16 miles to the south, and in the eastern Mendips 
Professor Reynolds has found similar Llandovery rocks. 2 An 
examination of rocks from the latter locality shows both in a 
1 Quart. Journ. Geol. Soc., vol. lvii. (1901), pp. 267-284. 
2 Quart. Journ. Geol. Soc., vol. lxiii. (1907), pp. 217-238. 
