90 Lacustrine Deposits in the vicinity of the Great Lakes. 
If the specimen of Sigillaria lepidodendrifolia figured by Brong- 
niart, Hist. Veg. Fos., tab. 161, were carefully examined, leaves 
like the above Aeuetibed would ‘probably be found. 
Among these specimens from Carbondale, are impressions of 
stems without any other marks than strie of different sizes, and 
others marked in various ways, with irregular protuberances and 
indentations. Several of these exactly resemble a stem figured 
by Goppert, (Syst. Fil. Fos., tab. 39, fig. 1, without remarks, ) and 
the outside bark of one of these being partially soa ay exhibits 
the impression of a beautiful Sigillaria, somewhat | e S. macro- 
discus, Brongn., on a very small and delicate idlen: 
Of these stems, and many other appearances from the fossil 
vegetation from this locality, it is quite impossible to give descrip- 
tions that would be at all intelligible without very well drawn 
figures. There are also several probably undescribed rgptinis 
dendra and Sigillariz. 
Arr. XII.—On the existence of certain Lacustrine Deposits, in 
the vicinity vi the Great Lae usually confounded with the 
“ Drift;” by I. A. Larnam 
_ OF all the subjects investigated by the geologist, none are more 
interesting or have attracted more attention within the last few 
years, than those relating to the diluvial, or drift and boulder for- 
mation ; and although much has been done to elucidate this 0 
scure point in the history of the earth, pes a vast amount of facts 
and observations has been collected and recorded, we are still 
5. 9 caged theory that will explain all the facts. One 
reason may be that no one theory can be found sufficient ; 
the ary sauiet be divided, and each portion may admit of a 
different explanation 
There is no doubt that much of what usually passes for drift 
in the region of the great lakes, must be attributed to a lacustrine 
origin of more recent date. ese deposits consist of nearly 
uniform layers of fine clay resting upon irregular beds of sand, 
gravel, boulders and hard-pan, constituting the true drift. The 
layers are from a quarter of an inch to three or four inches in 
thickness, and lie nearly horizontal—not conforming with the 
irregular layers of drift. The beds sometimes nishiti a thickness 
of fifteen or twenty feet. It is evident that these layers were 
deposited when the water was calm, and not subject to those vio- 
lent agitations that existed during the deposition of the drift. 
attentive examination of facts connected with the action of 
the waters of the present lakes, may throw some light upon this 
interesting subject. - 
