1 hy BOTANICAL GAZETTE [SEPTEMBER 
head of the tidal parts of its rivers. This is finely shown by the 
levels taken on the Misseguash by the engineers of the Marsh 
Company, of which a condensed compilation is given herewith 
(fig. 3). Where the heads of the rivers wander, as they are 
particularly liable to do on account of the struggle between the 
fresh water and the dam at head of tide, a large part of the 
marsh may be thus elevated at tide-head, and in consequence the 
drainage above it is greatly obstructed. This results in a great 
accumulation of fresh water, with a consequent formation of 
immense bogs; and thus have originated the great bogs at the 
heads of the Tantramar, Aulac, Misseguash, and LaPlanche. 
A 
Fic. 3.— True levels on marshes and bogs determined by spirit-level, condense 
from the plans of the Misseguash Marsh Co. Marsh is dotted and bog is shaded. 
The horizontal line is average high water in Cumberland Basin. Breaks in “ marsh 
are where the levels ran along the river. Vertical scale 40 feet =1 inch; horizontal 
¥% inch=one mile. A, from the Misseguash River near the railroad to Round Lake 
(fig. 2). 8, from the La Planche River near the railroad to Long Lake; C, from 
Cumberland Basin to Long Lake. 
Bogs therefore exist along the margin of upland, between rivers 
in the same basin,’3 and at the heads of rivers. Their extent, 
and their position relative to the cultivated and salt marsh may 
be learned from the accompanying map ( fig. 2). In a general 
way the head of tide on the rivers, that is, the highest part of 
the marsh, marks the transition from marsh to bog; above this 
point, the rivers are fresh-water streams meandering through 
bog and expanding here and there into lakes. 
The merging of the marsh into bogs is of course very gradual, 
and it is a well-known fact that the marsh mud extends every- 
*3O£ which a perfect example occurs in the “Sunken Island” between the Tan- 
tramar and the Aulac (fg. 2). 
