Geology of England and Wales,''"' ^c. 22o 



granted. But it may be asked, "how are we to account 

 for such a surprising accumulation of vegetable matter ar- 

 ranged in repeated strata (sometimes to the number of six- 

 ty and even more in a single district) separated from each 

 other by intervening deposites of clay and sand ?" Let us 

 hear these authors in reply. 



"Now the partial filling up of lakes and estuaries offers 

 us the only analogies in the actual order of things with 

 which we can compare the deposites of coal; for in such 

 situations we often find a series of strata of peat, and some- 

 times submerged wood, alternating with others of sand, 

 clay, and gravel, and presenting therefore the model of a coal 

 field on a small scale, and in an immature state." p. 346. 



Dr. Mac Culloch has instituted a series of experiments 

 to ascertain the nature, and account for the formation of 

 coal. The following are the general results to which they 

 conducted him. 



" Examining therefore the alteration produced by waiter 

 on common turf or submerged wood, we have all the evi- 

 dence of demonstration, that its action is sufficient to con- 

 vert them into substances capable of yielding bitumen on 

 distillation — That the same action, havingoperated through 

 a longer period, has produced the change on the brown 

 coal of Bovey is rendered extremely probable by the geog- 

 nostic relations of that coal. From this to the harder lig- 

 nites, surturbrand and jet, the transition is so gradual, that 

 there seems no reason to limit the power of water to pro- 

 duce the effect of bituminization in all these varieties, nor 

 is there aught in this change so dissonant from other chem- 

 ical actions, as to make us hesitate in adopting this cause."- 

 GeoL Trans. Vol. 2. p. 19. 



Dr. Mac Culloch, however, does not decide positively, 

 that beds of bituminous lignites were changed into coal by 

 the agency of water alone. By the application of heat to 

 jet under compression, it was fused into perfect coal ; and 

 he admits, that this might have been the proces* through 

 which the beds of coal, found in the earth, have passed j 

 though of opinion, that the agency of water is all that is ne- 

 cessary to account for the change: and Mr. Conybeare 

 does not "consider this as a sufficiently 'dignus vindice no- 

 dus' to evoke the god of fire for its solution." 



The coal measures are remarkable for the great abund- 

 ance of vegetable remains found in them; the animal rel- 

 VoL. VII.^No. 2. 2» 



