Ur, Maclure.on the Geology of part of N. America. .99 
The utmost stretch of i imagination or conjecture can form 
no idea of any period of time, when that primitive chain of 
mountains called the Alleghany, did not exist; but direct 
analogy, and perhaps logical reasoning, 
to conjecture that there must have been a period, ough 
beyond the date of our records, when neither the alluvial of 
the ocean, nor the Transition or Secondary Peo & cov- 
ered or overlaid either. side of said range of mountai ins 
thatthe chain of mot 
and from the nature of go pengenon which we now ea 
covering each side, we may have a right to conjecture that 
it was surrounded by water ; into gt run all the rivers 
that drained said mountains, forming channels deep in pro- 
portion to the immense length of time they may have run, 
and consequently much more profound than the channels 
One afterwards wore in the level country at the foot of the 
ountains on the retreat of the waters ; at this preeen time 
all tho: welers Saat t fall into that immense t est os 
Alle Ge -say minchnggun onc ins ; by 
sissippi and St. Lawrence, and a small part n w by ‘the 
Hudson, although it is probable that formerly a reinier pro- 
portion used to pass by that channel; these then are the 
only rivers that break through the whole chain of the Alle- 
ghany mountains, and run into the ocean, 
fon a review of an sesiiien series of phenomena, it is 
permitted to form conjectures on Y the past, and to look back 
on the probable changes, that may have preceded the pres- 
ent state, we presume that the situation of this continent 
will warrant such conjectures, and we should be naturally 
led to suppose, that at some former period, the continuity of 
the great chain of mountains was unbroken, by any o of the 
three rivers that now drain the great basin ; ; and that the 
waters confined by the high surrounding ridge would form 
an immense lake, the surplus of which would naturally fall 
over the ridge into the ocean, and would in the course o: 
time cut those se passages, which would drain said lake, and 
leave the great interior basin, with all its secondary or de- 
Position formation, as we now find it: as the waters that 
would fall over the ridge into the sea, must have previously 
left the ap eagle i ge lake, there would be little or no 
matter fit for allu ositions; and more probably that 
great alluvial re “an the bay of Mexico to Long- 
