30 L. Lesquereux—Coal Beds of the Rocky Mountain region. 
tion. But even if the lignite beds were proved to be of little 
horizontal extent, this would be no objection against the sup- 
position of their*origin as peat deposits. The emerged peat 
ormations are generally of this kind. It is teed the general 
case that peat bogs now cover hollows of limited areas rather 
than wide surfaces. Tie peat bogs formed in water along the 
shores of lakes or near the mouths of great rivers, are onl 
occasionally of wide extent. The deep pes bogs of Germany, 
i is found heaped by 
the growth of successive forests to the depth of seventy to one 
hundred feet, are mostly deposits covering from one to ten 
acres of ground. 
2d. I can say, from repeated and perschal observations, that 
most of the lignite beds of the west which have passed under 
examination have the under clays full of rootlets or of roots 
of the floating plants which were the first, generally at least, to 
contribute to the formation of the bed of combustible material 
by their debris. At the Raton Mountains, at Cafion City, at 
measures, or the Stigmarza, are ot roots but foating I leaves. 
And even their cylindrical stems are rarely found in clay beds: 
only their leaves fill them, just as the — of water plants 
fill the clay of the Tertiary Nignite. It is, however, a fact that 
some of the lignite clay beds, and diese. of the Coal-measures 
too, are clean or without admixture of vegetable remains, even 
of rootlets. But, when the peat is beginning its growth ‘at the 
surface of a somewhat deep basin of water. whose bottom 
been rendered impermeable by the deposit of clay (which always 
precedes the deposit of woody materials), this surface peat is 
often thick and compact before it is forced down and comes 
in contact with the clay; and in that case, therefore, the clay 
is pure or is not penetrated by roots or rootlets. 
he theory of formation by drifted matter = give 
explanation of this fact: that the bottom clay is sectenlle 
