60 THE POPULAR SCIENCE MONTHLY. 



Such formations are of frequent occurrence in the coal-measures, 

 in alternation with the seams of coal and the marine deposits left by 

 the overflow of the sea, and this was doubtless their origin. The fos- 

 sil forests which have been discovered in the same regions may be 

 similarly accounted for. The trees growing around the perimeters of 

 the lagoons would be partially submerged by the overflowing water, 

 and the sections of them buried in its muddy dejjosit would be left to 

 decay and fossilize in it. The persistent root-stocks of the sigillarias 

 and calamites, unharmed by the flood, would send up new aerial stems ; 

 and most of the other plants, having the power of sending out adven- 

 titious roots from their trunks, would be able to live and continue to 

 grow by that means, leaving their old lower parts to die, while they 

 lifted themselves, as it were, bodily up with the ascensional movement 

 of the soil. Several examples of such successive emissions of roots 

 are figured in the "Memoire." M. Grand' Eury has assumed that 

 the concurrence of two principal circumstances, acting coincidently 

 and in combination with each other, contributed essentially to the 

 formation of coal. One was the transportation by water for short 

 distances of all the vegetable matter of a region to be spread out flat 

 and stratified at the bottom of the lagoon destined to receive it ; the 

 other was the exposure of the matter, previous to this process, in the 

 open air to a certain amount of decay, of the nature and effects of 

 which he has made a patient analysis. From these principles he has 

 deduced a theory which may be summarized thus : The water which 

 served as the vehicle for the vegetable matter, which must have been 

 perfectly clean, because it was free from all mud, strong enough to 

 carry along its drift, and plentiful enough to sweep all the points of the 

 wooded region, could not have been any other than rain-water shed 

 upon slopes pronounced enough to make it easy for it to run and carry 

 the vegetable residues along with it, yet level enough not to allow the 

 ground to be cut up. The land over which the water flowed must 

 have been covered with a mass of plants and accumulated fragments 

 abundant enough to furnish much flotsam matter, and matted enough 

 to prevent its eroding the subjacent soil. The water must have been 

 intermittent, else the fallen trunks of trees and the fragments of every 

 kind which lay scattered over the ground would not have had time to 

 undergo the partial decomposition and disaggregation of their tissues 

 which necessarily preceded complete submersion. There must have 

 been, then, if not real seasons, intervals of relative calm, in which the 

 decomposition could have taken place, to be succeeded by times of 

 protraoted and extremely violent precipitation. The fact that a trans- 

 portation and deposition of the parts took place is attested by the 

 stratified structure of the coal. In both the coal and the schisto-car- 

 bonaceous laminae, all of the fragments, down to the most delicate 

 isolated organs, are always, with only the rarest exceptions, spread out 

 flat, and cemented one over another, lying together like the leaves of 



