AIR-BREATHERS OF THE COAL PERIOD. 287 



and in such places the deposit formed must contain a mixture of 

 land plants and marine animals with salt grasses and herbage — 

 the whole in situ* 



These considerations serve, I think, to explain all the apparently 

 anomalous associations of coal plants with marine fossils ; and I do 

 not know any other arguments of apparent weight that can 

 be adduced in favor of the marine origin of coal, except such as 

 are based on misconceptions of the structure and mode of growth 

 of sigillaroid trees and of the stratigraphical relations of the coal 

 itself.f It is to be observed, however, that while I must maintain 

 the essentially terrestrial character of the ordinary coal and of its 

 plants, I have elsewhere admitted that cannel coals and earthy 

 bitumen present evidences of sub-aquatic 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 condi- 

 tions it is evident that Sigillarice and their contemporaries must 

 often have been placed in conditions unfavorable 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. 



* In the marshes at the mouth of Scarborough River, in Maine, chan- 

 nels not more than a foot wide, and far from the sea, are fall of Mussels 

 and Myas ; and in little pools communicating with these channels there 

 are often many young Limuli, which seem to prefer such places, and the 

 cast off shells and other remains of which many become imbedded in 

 mud and mixed with land plants, just as in the shales of the coal mea- 

 sures. 



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

 the knowledge of the geological features of the coal, a sufficient acquain- 

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

 conditions neeessary 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 Sigillaria could not have lived with their 

 roots immersed in salt water ; that the chemical character of the under- 

 clays 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 formation of the coal. 



X Journal of Geol. Socy., vols. X and XV and " Acadian Geology." 



