602 



ME. J. EADCLIEEE 01ST GROOVES AXD 



flattened, and level with the top of the coal-seam ; it is 

 rough, angular, and pitted with holes from three eighths 

 to three quarters of an inch in depth, on its sides and 

 end. 



No. 3 boulder (fig. 3) found on the top of the coal-seam, but only 

 partly imbedded in the coal, the other part in the roof, the 

 layers of which were parallel on each side of the boulder ; 

 the top and one side flattened, sub angular, the carbonaceous 

 coating mixed with iron pyrites. 



No. 4 boulder (fig. 4), very smooth and round, found entirely 

 covered by the coal, the top of the boulder being six inches 

 below the top of the coal ; where this occurs the coal cover- 

 ing the boulder is of an inferior character and shaly, often 

 mixed with thin partings of dirt and shale. 



No. 6 boulder (fig. 5) found resting on the coal-seam, a little 

 imbedded, and partly surrounded by coal-shale, and covered 

 with the roof, same in kind as the surrounding strata ; sur- 

 face smooth. 



Por the following details of the mineral composition of these 

 boulders, I am indebted to the kindness of Professor Bonney, F.R.S. 



No. 1 boulder weighs one hundred and sixty-six pounds, and is 

 " a quartzite, grains mostly angular, some subangular, a few mode- 

 rately rounded, maximum about "027", but the majority about half 

 the size ; occasional small grains of chalcedonic aspect, such as 

 might come from a very minutely granular quartzite, a vein, or a 

 fine-grained schist. There are besides some small opaque grains, 

 probably iron-oxide, a few of a mineral resembling a rather dirty 

 epidote, and two or three of tourmaline, with some flakes of white 

 mica, and perhaps a little felspar." 



No. 2 boulder weighs one hundred pounds. " A hard quartzose 

 grit, composed of fragments much about the same size and shape as 

 in the last : but in these there is a larger proportion of, the chalce- 

 donic quartz, which sometimes strongly suggests a derivation from 

 a very fine-grained schist. There is also a considerable number of 

 brown earthy-looking grains ; these may be decomposed felspar, but 

 many of them have much more the appearance of a decomposed de- 

 vitrified rhyolite, though not of a very acid type ; some may be com- 

 pact argillites. The evidence as to the nature of these is hardly 

 conclusive. The slide contains a very few flakes of mica, and a 

 grain or two of epidote, hornblende (?), and tourmaline, but fewer 

 than in the last case." 



No. 3 boulder weighs four pounds. "A fine-grained grit formed 

 of fragments commencing about '005" in diameter; angular in 

 shape, consisting of quartz, a felspathic substance (as to the exact 

 nature of which it is difficult to pronounce), about equal in quantity 

 to the quartz. There are flakes of mica, green-coloured and white, 

 granules of iron-oxide, and, as before, one or two grains, probably 

 epidote and tourmaline." 



No. 4 boulder weighs twelve pounds. " A rock very similar to 



