1909] Bartlett, Submarine Bog at Woods Hole 235 
of at least sixteen feet, (probably more), since the first peat was laid 
down. Only two other suppositions could possibly be made: 1) that 
the Chamaecyparis grew in sixteen feet of water (!), or 2) that the 
water table sloped away from high tide level and was sixteen feet below 
it at a distance surely less than half a mile from the sea. The latter 
proposition is almost as absurd as the former, since in the loose drift 
deposits of the Cape Cod district the water table reaches the surface at 
approximately high tide level, and its gradient is always toward the sea. 
In Shaw’s paper (l. с.) bog “x” is described as a Chamaecyparis 
forest on a floating mat, covering a pond, the center of which is still 
open water. ‘That this is not correct has already been pointed out. 
The condition of this bog is not that of youth, but of old age. Оп 
account of the fact that it is not far above sea level, the surface of the 
water table, approaching sea level as a limiting state, has remained 
almost stationary, while the land has subsided. ‘The growth of peat 
has not kept pace with the (relative) rise of the water, and the result 
is that the bog is being drowned. ‘The pond at the center is increasing 
in diameter and water stands two or three feet deep among the trees 
during much of the year. "l'his bog is as truly a record of the subsi- 
dence of the region as the Quamquisset bog. 
From a study of the Quamquisset bog a very rough idea can be 
gained of the rate at which subsidence has taken place. If we accept 
Shaler’s estimate of a tenth of an inch a year as the rate of peat deposi- 
tion (under varying conditions it may be much more or much less than 
this), a period of approximately 2300 years would have been required 
for the growth of sixteen feet of peat below high tide level (zones A-D) 
and three feet above high tide level (zones D-F). If we assume that 
during this time the subsidence has been the logical minimum, sixteen 
feet (i. e., that the bottom of the bog when peat began to form was at 
high tide level, — an improbable supposition) we obtain as the rate of 
subsidence eight and a half inches per century. This estimate 
accords with that reached by Prof. C. A. Davis, who has made in- 
vestigations at other points on the New England Coast. А brief 
statement of his views in regard to the botanical and geological history 
of the New England salt-marshes has already appeared,’ but а more 
complete account may be expected in an early number of Rhodora. 
WasniNaTON, D. С. 
1 Bull. U, S, Geol. Surv. 376 (1909) pp. 19-20. 
