368 Br. E. Greenly— 



Conygar nothing but the Coal Measure sandstone, have been observed. 

 In every case the blocks are derived exclusively from the formation 

 against whose crags they rest. The breccias have, in fact, so far, 

 the characters of a talus or scree. 



They differ, however, from a pure talus in that the blocks are 

 embedded in a matrix of ruddy brown, loamy sand, sufficiently 

 compacted to leave a good hollow cast when they are taken out, 

 and occasionally even cemented by secondary calcite into a tolerably 

 hard rock. Now, this sand is not of local origin. It consists for 

 the most part of quartz, but is decidedly poor in white mica. When 

 washed it always yields a tail of heavy minerals (which are 

 enumerated below) and sometimes a front of light ones. The light 

 front consists of thin flakes of land-shells and black carbonaceous 

 debris. The matrix of the Conygar breccias, however, ia spite of the 

 fact that the Coal Measure sandstone upon which they rest is rich 

 both in white mica and in coaly debris, contains no carbonaceous 

 matter, and no more white mica than we find at Holly Lane, where 

 the breccia rests against the Caninia oolite. The heavy minerals 

 are the same at Holly Lane as at Conygar, and could not possibly 

 have been derived from the Caninia oolite. Thus it is clear that the 

 breccias are local screes, with a matrix of sand which is of alien 

 origin. 



The Stony Sands. — By simple waning of the blocks the breccias 

 graduate into stony sands, the blocks being still angular but of 

 smaller size. In the simpler sands they nearly disappear, but no 

 sand is completely free from blocks. Close to any crag they are as 

 local as in the breccias, but in the broad valley bottoms blocks from 

 the opjjosite slopes begin to appear, and in places equidistant from 

 crags of different rocks, they are derived ia approximately equal 

 numbers from the two sources. 



The Loamy Sands. — The composition of all the sands is essentially 

 the same, save that the light shell and carbonaceous debris may be 

 absent, being much greater at Holly Lane than anywhere else. 

 Some flocculent clayey matter is always present. There is the usual 

 overwhelming quantity of quartz and the same poverty iia 

 white mica. Nor is there much felspar. Some fragments of a very 

 fine siliceous mosaic, often containing black dust (apparently 

 carbon), may be regarded with confidence as Carboniferous chert. 

 The heavy residues are mainly composed of zircon, tourmaline, 

 garnet, magnetite, and rutile. Staurolite is not rare, and there are 

 small quantities of andalusite, biotite, green hornblende, epidote, and 

 ilmenite, Avith (I think) a very little monazite. 



Some of the quartz is clear, but much of it is dusky with inclusions, 

 and inclusions are abundant also in the garnets and in some of the 

 tourmalines and zircons. The larger grains of quartz are well rounded, 

 with dull, dry-rubbed surfaces, but nearly all the smaller grains 

 are angular. A few, however, show facets of secondary outgrowth, 

 as if derived from Triassic sandstones. The zircons, tourmalines, 



