L 
J 58 
liiiifs'-! nti tiio liver. .!cven or eii^ht miles above Clark's Ferry, its bed 
bo;^i!is to be ciosscd by batiks ofslaty and schistctse rock, wbich ob- 
.'^trijct its course. At tbe Great Fall*, tbree miles above Clark's 
Ferry, these obstructions rise from four to fifteen feet above the bottom 
of tbe stream. I'be bed of tbe Susquebaniiab to Harrisburj^, is em- 
barr-assed by these scbistose banks, wbirii ri-oss it, and belong to tbe 
ri{!;?e of Peter's Dsountain, tbrougb wbicb t!ic river forces its passage- 
Ali the valleys which we have just mentioned, have a strong solid 
'}.)tt(»m, favora!»!c for works of this nature; the Hoods ot" their rivers 
ih) not rise so high as in those which fall from tiic western side of the 
Alh'ghaiiy, but they flow all the year, and arc never dried up in the 
'^vannest seasons. 
From Hari-isbwrg. t'^c route of the ca.nal might proceed to Middle- 
■own, at the mouth of tiie Swetarra. Ilut i'rom thence to the Ches- 
apeake, the banks of the Susquehanuah beronic ditUcnlt end rugged; 
this consideration ha'; led to such a passage to the Atlantic, towards 
tlse cast by the Schuylkill. 
To promise a suiiicient snppiy of water fortius section, and shortei^ 
Its (listau'^c, it is necessary to keep as much as possible to the south 
of tiic road from Middictown to Philadelphia, by Lancaster and Dow- 
jungtown; thus the line of the canal will intersect the chief tributaries 
of the Susqucisannali below Middictown, and those of the Delaware 
i)c]ow' Philadelphia: nevertheless, as it crosses them near their heads, 
it is doubtful whctlier in the dry season they will su])])ly water enough 
for an active navigation, especially if we consider that they run over 
a stratunj of calcareous soil, which will frequentlyoccasion consider- 
iible iiltration. Particular attention should be paid, in tracing this 
scctio)!. to measure the springs which must feed it, and its line must be 
kept as loYv' as possible to admit as many streams as the localities 
will alknv. In any case, one tunnel will be indispensable at Gap 
Tavern, throiigh the Mine j-idge, which divides Octorara creek from 
Peguea creek: for the lowest depression of this ridge is 587 feet above 
the ocean, and 290 above the Susqnehannah at Harrisburg. 
This gap will thus be the summit level of the section of canal from 
Harrisburg, to the Schuylkill, and its tunnel must be kept lov/ enough 
to receive a sufficient supply of Avater to allow the level w hich descends 
on the oiie side, to Middletown. and on the otlierto the Schuylkill, to 
receive also their supplies; and to avoid more summit levels in this 
section of the route, these requisite conditions will compel to open two 
other tunnels on tiiis )*oute: the one east of the first between the heads 
of the Octorara and Buck-run, ihc other west: through the ridge which 
divides the little Conestago, from the Big Chickisalengo. The total 
sciigth oi' the three tunnels which will probably be required on this 
soction will be abor.t £ miles. 
These important facts, relative to this section, results from the 
if vets, performed nnder the direction of the Pennsylvania Commission- 
<"!•«, after concluding the reconnoitering, tour which we made together. 
^V(^ v.ill r.ow examine the results of the surveys, which the advanced 
