THE OLDEST AIR-BREATHERS 299 



aquatic origin of coal, except such as are based on misconcep- 

 tions of the structure and mode of growth of sigillaroid trees 

 and of the stratigraphical relations of the coal itself.^ It is to 

 be observed, however, that while I must maintain the essen- 

 tially terrestrial character of the ordinary coal and of its plants, 

 I have elsewhere admitted that cannel coals and earthy 

 bitumen present evidences of subaquatic deposition ; and 

 have also abundantly illustrated the facts that the coal plants 

 grew on swampy flats, liable not only to river inundations, but 

 also to subsidence and submergence.^ In the oscillation of 

 these conditions it is evident that Sigillarice and their con- 

 temporaries must often have been placed in conditions un- 

 favourable or fatal to them, and when their remains are 

 preserved to us in these conditions, we may form very incorrect 

 inferences as to their mode of life. Further, it is to be 

 observed that the conditions of submergence and silting up 

 which were favourable to the preservation of specimens of 

 Sigillarice as fossils, must have been precisely those which 



^ It is unfortunate that few writers on this subject have combined with 

 the knowledge of the geological features of the coal a sufficient acquaint- 

 ance with the phenomena of modern marshes and swamps, and with the 

 conditions necessary for the growth of plants such as those of the coal. 

 It would be easy to show, were this a proper place to do so, that the 

 "swells," "rock faults," splitting of beds, and other appearances of coal 

 seams quite accord with the theory of swamp accumulation ; that the 

 plants associated with Sigillarice could not have lived with their roots 

 immersed in salt water ; that the chemical character of the underclays 

 implies drainage and other conditions impossible under the sea ; that the 

 composition and minute structure of the coal are incompatible with the 

 supposition that it is a deposit from water, and especially from salt water; 

 and that it would be more natural to invoke wind driftage as a mode of 

 accumulation for some of the sandstones, than water driftage for the forma- 

 tion of the coal. At the same time it is pretty certain that such beds as 

 the cannels and earthy bitumens which appear to consist of finely com- 

 minuted vegetable matter, without mineral charcoal, may have been de- 

 posits of muck in shallow lakes or lagoons. 



2 foiirnal of Geol. Socy., vols. x. and xv., and "Acadian Geology." 



