362 Origin of Carbonaceous Shales. 



These very dilfereiit examples of the operation of causes now 

 in action would give us strata similar to those we have been 

 studying ; but we look in vain over the earth's surface for any 

 illustration or confirmation of the theory which attributes the 

 great stores of carbonaceous matter contained in them to the 

 spores or j)ollen of plants. 



Because the enduring sporangia of lycopods have remained in 

 considerable numbers in the carbonaceous mass derived from the 

 trees which bore them, and as sometimes these sporangia are the 

 only definite forms visible to the eye, the theory has been proposed 

 that to them chiefly we owe the accumulation of carbonaceous 

 matter that we call coal ; but the difficulty has been already sug- 

 gested that these sj^ores must have been associated with a thousand 

 times more plant-tissue; and as they nowhere form more than a 

 thousandth part of the mass, we cannot credit them with being 

 the sources of the combustible. The j^i'obable cause of their 

 abundance is, that they alone have preserved their forms, while 

 other tissues have been disintegrated. The perfect preservation 

 of the sporangia in the cones of fossil Lycopods, — Lepidostro- 

 bus, Flemingites, etc., — show how resistant to decay they are. 



It should also be said, that in some cases the spores of plants 

 may have accumulated in local masses, like the masses of seeds 

 and nuts in the lignites of Brandon, Vermont, and of Saltzhau- 

 sen in Germany. 



The annual dissemination of pollen in the cypress swamps 

 affords no good arguments in behalf of this theory ; for though 

 for a brief moment of the year somewhat abundant, scat- 

 tered widely by the winds, and conspicuous for its color, it has 

 attracted attention, no one will claim that any considerable 

 portion of the accumulations of carbonaceous matter which are 

 now taking place in or around the cypress swamps is derived 

 from this source. 



The composition of bituminous shales may be inferred from 

 the following analyses, made from specimens taken from several 

 geological horizons : — 



