Mofe—On Coal and Cannel. 209 



composedj so tiiat coal was more like consolidated lignite. It is, 

 however, difficult to conceive how, in the saro.6 bed the vegetable 

 matter could have been first partially decayed, then a layer thoroughly 

 rotted, and then another only partially decomposed ; and yet, if this 

 theory be correct, such must have been the case where the two va- 

 rieties are interstratified, as they are found near Blackrod in the 

 Wigan coal-field. 



But there is in most, if not in all, cases a well-marked distinction 

 between coal and cannel. Though they both are undoubtedly of 

 vegetable origin, the fossils found in them difi^er. In the hody of 

 the coal itself, what fossils are found are almost, if not entirely, vege- 

 table, whilst in the cannel, at least in that of Lancashire, fish- 

 remains not unfrequently occur. Beside's this, in the destructive 

 distillation of cannel for gas-making, it is necessary to have the 

 pipes from the retorts much larger than when common coal is em- 

 ployed, because, in the former case, these pipes are very liable to 

 become choked by a deposit, which at first was supposed to be pitch, 

 but which on examination is found to be formed of crystals of cliloride 

 of ammonium, agglutinated by tar, from which they may easily be 

 washed out and re-crystallized. May not this large quantity of chlQride 

 of ammonium be accounted for by the cannel bed having been dejDO- 

 sited in saltwater, the habitat of the fish found in the cannel ; the 

 seawater furnishing the chlorine for this salt. I am fully aware 

 that the distillation of common coal gives salts of ammonium, but they 

 are principally carbonate, sulphate, and sulphide with very little 

 chloride, and these are ail found in what is technically called the 

 ammoniacal liquor. The cannel also gives these salts in solution in 

 the liquor in addition to the crystals sublimed into the pipes as 

 above stated. 



There would be nothing very unreasonable in supposing the 

 growth of a rank vegetation in a swamp on the margin of an 

 estuary, sufficient to form a bed of coal ; that this, either by sub- 

 sidence or by the breaking of a bank, became covered by the sea, 

 and from a fresh became a marine swamp like the mangrove swamps 

 of the tropics (under which fish feed), and thus accumulate another 

 stratum under seawater, and probably from a different class of 

 plants, until by some fresh alteration of level or by the acumulation 

 of another bank to exclude the sea, the original state of things was 

 restored and another freshwater deposit is formed. There might 

 then be a bed of cannel between two beds of coal, and that such 

 alterations of levels may take place, or have taken place, can scarcely 

 be doubted by any geologist. 



It does not appear possible, under the supposition that coal results 

 from transported materials, to account for the interstratification 

 above referred to. 



Possibly, in some instances, independent beds of cannel may Lave 

 been derived from a deposit of sea- weed, such as the great weed-bed 

 of the Atlantic. 



VOL, JII. — no. XXIII. 14 



