174 BOTANICAL GAZETTE [SEPTEMBER 
The origin of the great bogs is thus made plain, but why are 
they mostly of the floating type? They are in fact almost 
entirely of this kind, though in places they are solid, and even 
approximate to the raised or Hochmoor type. They quake when 
one walks upon them, and a stick thrust through them pene- 
trates from one to four feet of moss, then goes through a foot 
or two of water and soft organic mud before reaching the solid 
marsh mud. The foot or two of water seems to be fairly con- 
stant everywhere except in the shallowest parts, while the thick- 
ness of the mat of floating moss increases from the shallower 
towards the deeper parts, as illustrated diagrammatically in 
fig. 4. The levels (fig. 3) also show that the surface rises as 
the bog grows thicker, asis tobe expected. It is a general rule 
in bog-formation over large basins that the floating bog is the 
first stage, and this is followed, as a result of growth and com- 
pacting, by solid bog, which in turn is succeeded by the raised 
or Hochmoor type. It may be a fact, therefore, that the float- 
ing character of these bogs is due to their youth —they have 
not yet had time to form the solid and raised types except on 
their oldest parts, around the margins andat the heads of the bog 
rivers, where such types do in fact occur. On this explanation 
one at first thought attributes the numerous lakes to places which 
the bog has not yet overgrown. But this explanation is in 
several respects not satisfactory. The facts seem to show that 
the growth of bog has been continuous from the upland outward 
to the marsh. Moreover, the lakes are always deeper than the 
surrounding bog. It seems, therefore, that there must be some 
positive factor tending to keep them open." 
“4 Possibly it may be connected with the presence in those places of a sufficient 
— of ue to prevent the formation of the strongly salt-shy (halophobous) bog vege- 
tation. As the efflorescence of salt on the mud Gicions up from deep in the bog by the 
dredge of the ae Company shows, some salt still exists in the mud beneath the 
bog water. This must be slowly dissolved out by the bog water, and the solution 
would settle towards the deepest places, which are the lakes, and might accumulate 
there toan extent sufficient, when stirred up by the waves, to keep them open of vege- 
tation. The meaning of the deeper places over which the lakes lie is not so plain, but 
probably they represent in part portions of oldriverchannels. This possible presence 
-of some salt in the bottom water of the bog cannot, of course, explain the floating 
character of the bog, since the lower layers of vegetation are dead and unaffected by it. 
A physiographic fact of some interest about the lakes may here be mentioned. 
j 
