"TR RIS TM 
224 Rhodora [DECEMBER 
hydrostatic pressure. The latter would bring about final equilibrium. 
High levels of the water table would sink, and low levels rise, until the 
pressure gradient from high to low levels balanced the resistance 
offered by the soil to the passage of water through it from points at the 
high level to points at the low level. This would be the condition of 
equilibrium. 
Applying these considerations to kettle holes, we see: — 1) that 
the water level in such a hole marks the lowest level in the water table 
of its drainage area, 2) that by replacing the kettle hole by a high 
hill, the same area might be made to coincide with the area of greatest 
elevation of the water table, and 3) that between these two conditions 
of the water table, any intermediate condition might be established by 
gradually filling the depression with a porous medium, such as soil or 
peat. The growth of a peat deposit in a kettle hole would continue 
until the water table lagged too far behind the bog level to provide 
sufficient moisture for preservation of peat from atmospheric oxidation. 
We may now turn to the bog which it is the special object of this 
paper to describe. 
As one walks along the shore from Woods Hole to Quamquisset, 
a salt-marsh is encountered which forms a prolongation of a slight lobe 
of the harbor. Its greatest width is about four hundred and fifty feet; 
its length perhaps twelve hundred feet. Seven hundred feet inland 
there is a constriction where the width is only about forty feet. So 
far as the vegetation is concerned, the seaward portion is a typical 
salt-meadow. Otherwise, however, it presents two anomalous features, 
in that it is neither penetrated by a tidal creek nor protected from the 
sea by a barrier beach. ‘The explanation of this unusual topography 
is disclosed at low tide, in a line of stumps and prone logs along the 
water's edge,— the stumps in the position in which the trees grew. 
These show that our salt marsh is a peat bog which the sea has invaded, 
not a tidal flat built up through the usual agencies of salt-marsh forma- 
tion. The stumps lie in the face of an escarpment only a foot or so 
high, formed by undercutting of the peat in which they are imbedded. 
At the surface the peat is protected from erosion by three or four 
inches of tough Spartina turf. At high tide this turf is submerged; 
at low tide a few feet of beach slopes gradually from the escarpment to 
the water. On the beach the peat is covered by a few inches of 
pebbles апа bowlders, thrown up by the waves. Plate 82 is from a 
photograph of the shore, taken at low tide. 
