288 Account of a Remarkable Fossil Tree. ' 
substance and thecale spar, were deposits from particles sol- 
uble, or intimately mixed with water, previous to the in- 
closure of the tree in its rocky envelope. 
P 
“ At the time of our visit (August 13, 1821,) the depth of | 
water upon the floetz rocks forming the bed of the river 
Des Plaines, would vary from one to two feet; but it will 
be recollected that it was ataseason when these higher trib- 
utaries, and the Illinois itself, are generally at their lowest 
stage. Like most of the confluent rivers of the Mississippi, 
os their tributaries, the Des Plainesissubject to great fluc- 
tuations, and during its periodical floods may be estimated | 
to carry a depth of eight or ten feet of water to the junction 
of the Kankakee. At those periods the water is also ren- 
dered turbid by the quantity of alluvial matter it carries 
down, and a search for this organic fossil, must prove unsuc- 
cessful. But during the prevalence of the summer droughts, 
in an atmosphere of little humidity, when the waters are 
drained to the lowest point of depression, and acquire the 
greatest degree of transparency, it forms a very conspicuous 
trait in the geology of the stream, and no person, seeking 
the spot, can fail to be directed to it. Although correspon- 
ding in its direction to the apparent course of the formation 
in which it rests, itforms an acute angle with the natural seams 
and fissures which chequer the surface of the rock 5 cand “0 
of the tree, have acquireda blackish hue, while os ee 
rock, being a light grey, presents a contrast that is 
te arrest the attention of the observer 
he sand stone rock in which this fossil tree reposes, is 
every where found in a horizontal position, and differing on-— 
ly with respect to ‘hardness, and colour,—points which do — 
notnecessatily ily. map a different formation. The remains of 
bodies in this stratum, are not abundant, oF 
organized 
have not been successfully sought ; and it appears to be 
wholly wanting in the various species ; of concholites so plen- — 
ufully imbedded in the calcareous formation which rests up- 
onit. It is probable that future observations will prove, 
that its organic conservata are chiefly referable to the vege- : 
table kingdom. It is certain, that this inference is , 
ed by 1 the facts which are before me, and particularly by the 
appearances of apes strata in the bed of _ 
river Des Plaines, where the imbedded walnut, is the 
