NATURAL HISTORY SOCIETY OF GLASGOW. 133 



coal-fields at present not included under the acceptation of the 

 term coal, which are charged to a greater or lesser extent with 

 similar organic products to those in the Torbaneliill land. These 

 are our paraffin oil shales — and they are now being eagerly sought 

 for in every district of our Scottish coal-field. 



. Every one knows that nearly all our ordinary seams of common 

 coal — such as the free, cherry, and sphnt coals, are now acknow- 

 ledged by geologists to have been formed from great accumulations 

 of vegetable matter that has grown upon the spots where these 

 coal beds now exist — somewhat like our present peat-mosses, only 

 the vegetation of the coal period was of a totally different kind 

 from that forming our present mosses. In our coal measures, how- 

 ever, we liave other varieties of coal besides those above-mentioned. 

 These are our cannel or gas coals. They differ in their structure 

 from ordinary coal, and show that the vegetable matter of which 

 they are composed did not always groAv upon the spot where we 

 now find tliem. They are the result, in fact, of deposits of fine 

 macerated vegetable matter, which has been swept off from certain 

 coal-tracks, and deposited in a sedimentary condition over the area 

 of some old sea or lake bottom. 



We find in our cannel coals what we hardly ever find in our 

 ordinary free coals — that is, the remains of certain shells, fish, and 

 fishcoprolites, clearly pointing to their sedimentary origin. Our 

 cannel coals also contain a much greater proportion of volatile in- 

 gredients, and are, therefore, more valuable for oil and gas-produc- 

 ing purposes. 



As the cannel coals during deposition were liable to get mixed 

 with other earthy matter, such as sand and clay, we therefore find 

 them of every degree of purity ; — that is to say, we find them ex- 

 isting in every variety — from that formed of a nearly pure vege- 

 table pulp, to ordinary bituminous shale, with a strong clayey or 

 sandy base, and with but a small amount of carbonaceous matter. 

 It is therefore very difficult, in some varieties, to say wliether 

 they should be considered as cannel coal, or bituminous shale — for 

 the question is often one of degree as to the amount of hydro- 

 carbon they may contain. It was this great difficulty that some 

 years ago led to that great law-suit as to what should he considered 

 a cannel coal, or bituminous shale; for the Torbaneliill cannel — 

 the disputed band in question — has a strong clay base. You all 

 know that tlie evidence adduced on Isoth sides was very unsatis- 



