150 G. W. Bulman — Drift Coal in Sandstone. 



placed on a smooth surface of the rock, rapidly produced gelatiniza- 

 tion, and that the jelly, when dried and treated with acetate of uranium, 

 developed abundant characteristic crystals of the double acetate 

 of uranium and sodium. The presence of a sodium-bearing mineral 

 in the rock was thus placed beyond doubt. By treating a section 

 with hydrochloric acid, and staining with fuchsine, after washing off 

 the acid, the nepheline-patches were fairly well defined. Finally, to 

 make quite sure of the matter, I sent a specimen of the rock to 

 Professor Rosenbusch, of Heidelberg, who was good enough to have 

 a very thin slice prepared, in which he succeeded in detecting the 

 presence of small four- and six-sided sections of nepheline. Prof. 

 Eosenbusch confirms my diagnosis of the rock, and refei's it to the 

 trachytoid division of the phonolites in his classification (Physio- 

 gropMe der massigen Gesteine, vol. ii. p. 622). 



The main portion of the rock is made up of small lath-shaped 

 crystals of sanidine, presenting in their mode of arrangement a 

 marked micro-fluidal structure. Porphyritic crystals of sanidine 

 also occur, but not very frequently. The only other constituent of 

 any moment is a green augite giving high extinction angles. The 

 presence of aegirine has not been detected. Apatite and sphene also 

 occur in isolated granules. In the nepheline-patches the alteration 

 of that mineral has given rise, as usual, to the formation of zeolites 

 (analcime and natrolite). 



Geological Survey Office, 28, Jermyn Street, S.W. 

 Feb. 20th, 1892. 



IV. — Drift Coal in Sandstone. 



By G. W. Bulman, M.A., 



C orbridge - on - Ty iie . 



THE most exclusive advocates of the hypothesis of the terrestrial 

 origin of Coal admit that those small irregular patches, veins, 

 and nests of the same occurring in beds of sandstone are formed of 

 drift vegetation. And admitting this, it is difficult to draw the line 

 until we have ascribed a similar origin to certain definite coal seams 

 of considerable extent. Granting this much, however, is obviously 

 a different thing from the belief that all coal seams are to be ascribed 

 to drift vegetation ; and while the following remarks are intended 

 to show what a strong argument such drift coal in sandstone fur- 

 nishes for the probable drift origin of certain coals, there is no in- 

 tention of ascribing such an origin to coal in general. 



Such drift coal in sandstone is of very common occurrence in the 

 Coal-measures, and good examples are to be seen in the coast-section 

 of the Northumberland coal-field. It seems strictly analogous to 

 those similar patches of shale which are also common in sandstone, 

 and the same origin must be ascribed to both. 



The explanation in the case of the shale is, that the currents which 

 brought the coarser material of the sandstone failed at intervals, and 

 that consequently the finer sediment — which would otherwise have 

 been carried further and laid down by itself — was allowed to settle 

 in hollows among the coarser, and was in turn overlaid by it when 



