Origin of ('arbonaceous Slialett. 350 



My object in now calling attention to this subject, is to point 

 out some difficulties in the way of the acceptance of this tlieory, 

 and to offer additional considerations in favor of the view ])re- 

 viously proposed, that the carbonaceous matter is mainly derived 

 from algae. 



It is true that in a great number of localities these minute 

 spheroidal bodies occur, but they are not always or even gene- 

 rally present, and strata many feet in thickness and miles in 

 extent may be examined without discovering any of them. 

 They now form but a very insignificant fraction of the carbona- 

 ceous matter of the shales ; and there seem to be good reasons 

 for believing that they have always done so. 



In the first place, they are apparently the organs of fructifi- 

 cation of plants, but these in quantity always bear an altogether 

 subordinate position to the vegetative tissues with which they 

 are connected ; and if it were true that the carbonaceous matter 

 of these shales was derived only from the reproductive organs, 

 we must account for the disa])pearance of the hundred times as 

 much organic matter which once composed the organs of vege- 

 tation. 



Second, it is one of nature's wise provisions that tbe 

 envelops of tbe embryo in plants should be specially resistant 

 to decay, as well as to the action of many destructive agents. 

 The testa of some stone-fi'uits is the hardest plant-tissue known, 

 and is si^ecially adaj)ted to resist mechanical violence. Many 

 of the smaller dru2:»es are eaten by birds and other animals, 

 which have the power to digest the sarcocarp but leave the 

 stone uninjured. So the spores are somehow much more en- 

 during than other tissues of the plants that bear them, and 

 are sure to be preserved out of all proportion to their quan- 

 tity. Hence we may conclude that the spores of lycopods 

 wafted from the land, or the spores of algae which sunk here 

 and there with the other materials of the shale, would be pre- 

 served, while at least all the cellular tissue of the plants would 

 be disintegrated, though perhaps not destroyed. 



Third, the great number of sea-weeds found fossilized in the 

 shale indicates the abundance of this class of vegetation and 

 possible source of carbonaceous matter. But the tissue of sea- 

 weeds is all cellular, is easily disintegrated, and has broken 



