GEOLOGY OF THE BRISTOL COAL-FIELD. 349 



difficulty examined by the microscope. jN'othing but a black 

 powdery mass of Carbon is seen which is perfectly opaque, so 

 that the observer is greatly discouraged with his attempts to 

 discover the woody fibre, medullary rays &c., so clearly described in 

 all microscopical works. 



It is only now and then that a good solid piece is found, that it 

 is possible to satisfactorily make out the vegetable structure by 

 section. The most successful way to proceed, that I have met 

 with, is to soak a piece of the Coal for a week or two, in a tolerably 

 strong solution of Potassium Carbonate (Pearlash,) then after 

 washing well in distilled water, to gently warm the specimens in 

 strong nitric acid till they change to a resinous brown color. They 

 must then be sliced with a thin sharp knife and then be mounted 

 in Canada balsam. On an examination of one of these sections, 

 three kinds of substances will be seen — an opaque black carbon 

 scarcely showing any structure, earthy matter slightly coloured, and 

 a yellowish red semi-transparent portion shewing the medullary 

 rays and fibres in the most beautiful manner. It is from this last 

 ingredient that the gas is produced, so that the greater per centage 

 of this there is in a sample of Coal, the more advantageous is its 

 use for gas works. 



The fossils that have been noticed in the Bristol Coal measures 

 are Conifers, Ferns and Club mosses. The author has not met 

 with a single mollusc or animal remains of any description except 

 in the Millstone Grit, this is probably owing to want of opportunity 

 for observation, as it is not likely so large an area of swamp as the 

 original forest must have been, should have had no aquatic animals. 



In the early part of this year Count Castracane of Eome, reported 

 to Mr. Sorby that he had discovered Diatomaceae in English Coal 

 ashes. Mr. Sorby reports he had seen on these slides several well 

 preserved species of Diatoms and also bodies like Xanthidia. I 

 have searched most diligently the Coal ashes of our Coal field but 

 quite unsuccessfully. The Count's Coal was shipped from 

 Liverpool. 



