1921] DACHNOWSKI—PEAT DEPOSITS 59 
The following pki deposits are representative of the subdivisions 
in the land-laid group, and will be reported in another paper: 
1. The New Haven Marsh near Plymouth, Ohio (glacial Lake 
Maumee type); the peat deposit southwest of Rome, New York 
(glacial Lake Iroquois type); and the Algoma Muskeag near 
Roseau, Minnesota (glacial Lake Agassiz type). 2. The Dismal 
Swamp west of Norfolk, Virginia (Pamlico coastal terrace type). 
3. The Kankakee Marsh, between South Bend and Crumstown, 
Indiana (in the Bloomington morainic system). It will be noted 
that peat deposits. are regarded here in their relative space and 
time dimensions. 
In regard to the stratigraphic units of peat deposits, reference 
may be made to Bulletin 802 (5) and left with this passing sug- 
gestion. Whatever system of classification of peat materials may 
be adopted, it will be found that for several reasons it cannot be 
carried uniformly and with constant value over so broad a territory 
as discussed here. The main difficulty arises from the unlike 
development of the vegetation unit which forms the layer of 
peat, and from modifications of the successional series in diverse 
geographic regions. Insensible gradations or phases due to varia- 
tions in composition of plant remains set a limit to the most 
refined botanical division of peat materials that can be recog- 
nized. 
Investigators approaching peat-land problems for the first 
time are apt to be influenced by the idea of permanence and fixity 
of specific limits. In a large measure this may be accounted for 
by the fact that the very recognition of such a thing as a type of 
peat material carries with it the impression of an entity, and that, 
if these characteristics are modified or supplanted by others, the 
unit in question no longer belongs to that type. The degree of 
individual difference admissible within a type is a matter of indi- 
vidual judgment. Variations exist within specific limits, but 
what these limits are is still a matter of diverse and constantly 
changing opinion, until these gradations and phases are measurably 
well established. No evidence of this sort of peat type limita- 
tion is available as yet, but the detailed application of ecological 
and instrumental methods strengthens the conviction that the 
