VOL. XIV. (1) THE PRESIDENT’S ADDRESS II 
probable that coal originated from this growth. Doubtless 
there is force in this argument, but, as I have said, our 
knowledge of all the forms of the Lepidodendroids is by 
no means perfect. Apart from this I do not know that 
the presence of Stzgmarza in the underclay sis proof 
positive that these fossils are the roots of coal-forming 
vegetation. If we take bogs we find trees growing in them. 
Further, itis by no means improbable that Lepidodendroid 
vegetation may have grown in the soil before the con- 
ditions were suitable for the bog-like growth of the coal- 
forming vegetation. 
Whatever the nature of the coal-forming vegetation, one 
thing is certain, viz., that the coal period was remarkable 
for an alteration of land—subsidence, re-elevation, or filling 
up, and fresh growth of vegetation on the successive land 
surface, each subsidence sealing up, as it were, a seam of 
coal. In other words, vegetation grew, became submerged 
and covered with detrital material such as we see sus- 
pended in the waters of large rivers of the present day ; 
then land again, or, at least, conditions restored which 
allowed the growth of vegetation, only to be in turn again 
submerged. So the process went on till, like all previous 
formations, the Coal Period came to an end and the Per- 
mian Epoch began, when a new condition of things 
prevailed. 
After submergence chemical processes set in, the vege- 
table mass underwent decomposition, and new compounds 
were formed according to the chemical affinities of the 
constituent elements: the result is the carbonaceous mass 
left in the form of coal. 
Such, then, was the order of things to which we are 
indebted for the coal we now consume, and in this con- 
sumption we return to nature the materials extracted 
from the atmosphere and soil of the Carboniferous 
Period. 
