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REPORT

THE BOARD OF ENGINEERS,

AS WELL AS THAT OF

W. E. LOGAN, ESQ.,

^ra&tncCal (StalaQiitt

UPON THB

smym of lake si. peter

IN OCTOBER, 1850.

MONTREAL:
PRINTED BY LOVELL AND GIBSON, ST. NICHOLAS STREET.

1850.

LETTER OF INSTRUCTIONS,

FROM THE

MONTREAL HARBOUR COMIIISSIONERS,

to THB

BOARD OF ENGINEERS,

APPOINTED TO SURVEY LAKE ST. PETER

Copy.

Montreal, 22nd October, 185(X
Gentlemkn, — Some five years ago, it was determined by
the Provincial Government of Canada, to improve the naviga-
tion of the St. Lawrence between Quebec and Montreal, so that
a vessel drawing 16 feet water, should be able to sail, up or
down, in any stage of the water. Mr. Atherton, in 1844, then
in the employ of the Provincial Board of Works, surveyed Lake
St. Peter, and reported in favor of deepening the present natu-
ral channel. This was opposed by the President of the
Board, Mr. Killaly, who advised the cutting of a new and
straight channel. This plan being adopted, the work was
placed under the superintendence of Mr. David Vaughan.
While this work was going on, a strong party sprung up,
who opposed the construction of this straight channel, which
they stated would be unsuccessful, and that at least 600
feet of a breadth, at its upper end, would be required — that
for the purposes of the trade, its very straightness was an
objection, &c. An outlay of some $320,000 had been made in
this new channel, when the Government, on the Reports of a
Committee from the House of Assembly, stopped the work in
1846. We would refer you to the Reports of Mr. Atherton,
Mr. Young, the Comm^tee of the House of Assembly, Captain
Bayfield, and Captain Boxer, R. N.

The deepening of Lake St. Peter, and the I'mprovenient of
the navigation, between this City and Quebec, is now i)lace(i
under our control, and we liave called on you, as gentlemen of
experience in your profession, to examine fully, into the vvholo
matter, and report to us, the best means, of eilectually opening
a channel, of 16 feet in low water, between this place and Que-
bec, as well as the cost of opening a channel of 13 fiet, 14 feet,
and 15 feet.

"We have placed at your disj^o.-al, two Bianch Pilots, Messrs
David Bouillie, Branch Pilot Ko. 2, Zephirin Mayrand, do. do.,
on whose statements you can rely, and who are prnetieally
acquainted with the towing of vessel?, and the various channeli*
and places which require dredging. A steamer is placed at your
disposal, and you will be supplied with boats, or whatever else
you may require in the survey.

The foregoing remarks we believe embrace the plain facts,
and as you are now acting as our Board of Engineers, without
and entirely unconnected, with local interests or prejudices, we
believe you will be enabled to arrive, at a comprehensive result,
and give us such a report, with your reasons for your opinions,
as shall have weight with those, who may desire to be convinced
of their correctness, before advancing, the necessary funds to
complete the work, this latter remark, is the more necessary,
from the conflicting views which exist on the subject.

We are happy to say that W. E. Logan, Esq., Provincial Geo-
logist, a gentleman of great eminence in his profession, will
accompany you, in the hope, that he may be of service in
determining, the character and age of the deposite in Lake St.
Peter.

"We are, Gentlemen,

Tours very respectfully,

(Signed) John Try, Chairman.
" John Young.
" Louis Marchand.]

To General McNeil, Captain Child, and S. Gzowski,

Board of Engineers to Examine and Survey Lake St. Peter.

Mo.VTRii.\r., 31st October, 18.50.
To The lion. The; Board of Harbor Commissioners of Montreal.

Geni'lkmkn, — Having accepted the responsible trust confided
to ns, as your Board of Engineers, we, on the receipt of your
instructions of the 22nd instant, proceeded to the discharge of
the duties devolved on us, as specified in those instructions.

Accompanied by your President and Secretary, experienced
Pilots provided, in fact with every facility essential to the speedy
and accurate attainment of our objeet, we embarked in the
steamer Richelieu that afternoon for Sorel — where we had the
pleasure to be joined by Mr. Logan and Captain Armstrong, and
early liie next day, (Wednesday, 23rd,) reached our main field
of operations. Lake St. Peter.

Under favorable auspices, the calmness and clearness of the
weather, and, consequently, sroothness of the Lake, we com-
menced soundings with a pole graduated to feet and inches, and
making such other surveys, examinations and observations, as,
in our judgment, would suffice to disclose with sufficient minute-
ness, all the facts, to enable us as you desire, " to arrive at a
comprehensive result, and to give you such a report, with rea-
sons for our opinions, as shall have weight with those, who may
desire to be convinced of their correctness, before advancing the
necessary funds to complete the work."

1st. — To ascertain the nature and character of the materials
forming the Bars and Flats which obstruct the navigation of the
River p.nd Lake, frequent borings were made, and specimens
preserved for analysis by Mr. Logan, to whose communication on
the subject (hereto appended) we would respectfully refer you ;
and from the tenor of which it may be conlidently assumed, that
the flats of the Lake are an alluvial deposit of a very fine clay
slightly intermixed with sand, formed by the river drifts of the
St. Lawrence, and its subsidiary arms, which meander through
the islands and debouche, at the head of the Lake, together with
the lateral tributaries, the Rivers Yamaska, St. Francis, and
others of less capacity.

It may be inferred, as experience h.is proven, that material of
sueh description is easily < Koavated by dredging and the use of
the harrow; and yet its consistency is such, that it does not

seem, from previous excavationM, to have silted op; obvious,
however, would be the necessity of concentrating the several
currents, as far as practicable, into one Channel, thereby mate-
rially aiding further excavations, and as a permanent security
against a re-deposit of obstructions once removed.

2nd.— We proceed to state the direction and character of
existing Channels, comparing the soundings and the velocities
of currents, of the Old and New Channels with each other as
determined by ourselves, and also by Captain Bayfield, R. N ,

and others.

The facts under this head are summarily exhibited in the fol-
lowing Table:—

TABLE Ist.

Shewing the Soundings taken in tiie Straight Channel, in the
years 1846, 1847, 1848 and 1850; also those in the Old
Ship Channel, all reduced to low water of 1 1 feet on the
Flats, the results being the mean depth in cross sections of
150 feet in width, commencing at the head of the cut for
the New Ciiannel and at the Upper Bar for the Old.

1846.

1847.

1848.

1850.

By Air. Keefer

and
Cap. Vaughan.

Capt Bayfield.

R. N.

By
Cap. McKim.

By
Mr. Rubridge.

Board of Engi-
neers, 23d, 24th
25th October.

Soundings

Old Ship Channel

Board of Engineers.

2
3
4
5
6
7

11 9J

12 2
12 5^
12 5^-
12 5^

12 9|

13 3
12 llf

n 5^

11 10

Captain Bayfield reports on 17th September, the depth to be
at least as much as previously reported, if anything increp-sed.
Again that there is no perceptible change in the relative depths
of the two Channels, for 16 years, or since his survey of the
Lake, in 1830, except at the head of the new Channel, where a
considerable portion of the former shallow bank has been cut
away by the action of the current, as shewn by the red dotted
line on the Chart

14 7i
13 8J
13 lOi
11 3

11 6f

12 8\

15
15 0^
13 7

11 11

12 lOf

13 6f
12 9Vr

12 3^

13 2

12 lOH

14 a
13 10
13 2
13 8

13 10
13 9
13 2
13 9

13 7

On the Upper Bar
1st mile, average lb
feet, 12^ feet mini-
mum. Thence a deep
Channel for 3 miles.

Thence for 2 miles
on the 5th and 6th
miles, 11 feet 8^ in.

Thence fur 1-2 or
to the 8^th mile, 11
feet 9} inches.

Thence for 1-2
miles, or to the 10th
mile, 12 feet 8^ inch,
on 10th mile, 13 feet
9^ inches, 10| miles,
13 feet 3 inches.

13 6^
12 6^

12 9f

The average depth of water in the Straight Channel, for a
distance of 2^ miles from the point to which dredging operations
were carried, is 12 feet 9 inches.

The " position of Soundings" hj Messrs. Keefer, Vaughan,
McKim and Bubidge, is more particularly stated bj localities

nnmtd by them, answering however very approxlinutely to the
ilistunces assumed above by us.

From the foregoing it appears that for a period of five years,
from 1846 to 1850, inclusive, the New Channel has, to say the
least, generally maintained the depth to which it had been
dredged. In I'act, '.t has increased in depth even beyond that
represented by thf, soundings of Mr. Rubidge in 1848, except-
ing for a sliort distance at the head of the Channel, where he
reports 10 inches to 1 foot more water than we do. This,
however, we do not deem material, as we tliink it easily accounted
for from the fact that the excavated sand of which that portion
of the cut is formed, although displaced in tempestuous weatlier
and by the currents, was yet too heavy to be far removed, and by
its gravity was soon deposited where it now is. This seems the
more probable, because of the generally increased depth of the
Channel below, where the bottom consists, as hereinbefore
stated, of a very fine clay, which, when disturbed, does not
readily subside, but mingles with the waters, and is carried off
by the current; in which supposition wo are fully supported by
the Report of Mr. Logan, which determined the light and floccu-
lent character of this clay, and which, in our opinion, fully
proves, that with proper concentration of currents and the appli-
cation of mechanical means, in the first instance, to disturb and
remove the material, permanency in the depth of any adopted
Channel will be secured.

TABLE No. 2.

Exhibits the compirative velocities of the currents in the old
and New Channels per mile, per hour: —

Old Channel

Below the Upper Buoy, 1 -58 per

mile, per hour.
Half way between the Lower

Light and Buoy, 0*67

At Lower Buoy, 0*81

New Channel.

At the head of New Cut, 1-45

Lower end, 0-59

One mile above Lower end of
Cut, 0-54

The velocity of the current at end of Stone Island in the Main Channel,
1 58 per mile, per hour.

It may be satisfactory to append, in connection witli the fore-
going, the following extract from the Unport of Ca[)tain liay-
lleld:

" Although the first cut is incomplete, anil has not been car-
*' ried much below the fith Buoy, a current of considerable
" strength has already been establislunl, fully eciualling, if not
" exceeding in rate, that which obtains in corresponding points
" of the Old Chaiuiel, for instance, at the 2nd liuoy of the
** New Channel, the rate was 1 i^ Knots, while, at the Upper
" Liglit^ it was 1| Knots; at the 7th Buoy, 'i Knots, and at the
" Lower Light Vessel, ^ a Knot. These facts show that there
'* is no tendency in the New Channel to fill up which is ab-
" scribed to the direction of tlio resultant of the currents of the
" Main b'trearas which unite a short dista ce below Stone
" Island, and also to the strong current setting to the Southward
" past the point of the marshes that extend from MonK Island,
" and lastly, by the action of the current, in cutting away the
*' banks between the red dotted line and the first Buoy, which
" southerly direction is deemed very important.

*' But with reference to the improvement of the Old Channel,
" it would be unsafe to leave the New Channel open, because
" the very considerable water now passing through it would
*' lessen the chance of any cut that might be made through it
" remaining open."

We concur with the above-named justly distinguished autho-
rity as to the existence of a current of considerable strength
through the straight Channel, and its probable increase, and
that there is no tendency to fill up; but we differ with Captain
Bayfield in the fact as stated by him, that a greater velocity of
current exists in the New than in the Old Channel. We find it
otherwise, as stated in the foregoing table, from the obvious
fact that from the direction of the waters of the St. Lawrence,
whether by the Main Stream, or through subsidiary Cliannels
among the Islands, and theincliurition not Southward but North-
ward at the head of the Lake, and after it has passed the marshes
extending below Flat Island, that the greater volume of water
would seek an outlet by the Old Channel, and the samecause
does operate in favor of the velocity, of current, in the Old
Channel throughout, unMl when, from the influence of currents

from the subsidiary Channels entering the Lake, North of the
Main Channel, a Southern inclination from the Lower Light
obtains to the junction of the two Channels opposite the
River Machiche.

We also agree w'th Captain Bayfield, that it would be unsafe
to leave the New Channel open, in the event of improving the
Old one, while the same course of reasoning, will, in our opinion,
justly apply to prove the necessity of stopping the Old Channel,
should the improvement of the New Channel be decided upon.

In addition to the foregoing considerations, it is proper, before
entering upon the estimates of the costs, to announce this prin-
ciple of concentration of water into our Channel, as the indis-
pensable guide to a conclusion, upon v/hich, we can ourselves
rely, and by which, the objects as stated in our instructions, viz.:
" The best meons of effectually opening a Channel of 16 feet
" depth in low water, through Lake St. Peter, as well as the
** cost of same, and also the cost of opening a Channel of 13, 14
or 15 feet," can be effectually and satisfactorily secured.

In fact, no one can doubt that much water now flows through
both Channels, diminishing the supply in each separately, and
as a consequence, if either were closed, the current through, and
depth of the other, would be proportionobly increased.

In connection then with cost of excavations to deepen either
Channel within prescribed limits, we must look to the practica-
bility and cost of effecting such a concentration.

For instance, if we would effectually improve the New Chan-
nel, we must direct the waters flowing through the subsidiary
Channels into the main Channel of the St Lawrence, and by the
construction of dams and jetties, direct the accumulated body
of water fairly into it, and also close the Old Channel.

If, on the other hand, the improvement of the Old Channel is to
be effected, the rame principle of concentration applies; we have
but to allow the waters of subsidiary Channels to flow on natu-
rally, for they chiefly come down in the desired direction, and
to complete the work of diverting the whole of the main current
of the ht. Lawrence to throw a groin in a north easterly direc-
tion from the Flats of Monk Island, and thence by a clam across
the New Channel, to the Bar, North of it.

With these considerations we have the means of instituting a

e
5',

comparison of the two Channels — or, rather, to determine in
what direction it may be advisable in our opinion to make a
Channel, answering the conditions specified in our instiuctions;
for, independent of all pre-conceived opinions and local preju-
dices, we regard either Channel, or both, as but natural features
to be availed of, so far onlj as they may not impair or conflict
with the main object — which object is the making of the best prac-
ticable Channel, through the Lake St. Peter. Unquestionably,
one or the other, the Old, or the New Channel, indicates where
the Channel in view should be, and to determine which shall be
adopted, we proceed to compare them.

It will be shewn that at each and all of the several widths
and depths assumed, the Old Channel has greatly the advantage
in point of cost ; nor does it appear unfavourably on comparison
of the soundings or the velocity of currents.

The New Channel being straight throughout, is about three
quarters of a mile shorter than the Old, which is termed crooked
by comparison; but which, nevertheless, is not, from all that we
can learn, inconveniently so, as to cause us to attach as much
weight to the objection, as obtained in the opinion of many others
of high authority. In other words, we are satisfied that were it
of the desired depth and width for large vessels throughout, the
inconvenience alledged would not be experienced. Ceriainly a
New Channel would not be sought as a remedy for obstructions
caused by River drift, which may bb removed as easily from the
one as the other.

In viewing this case de novOf we cannot but observe that
nature should be aided by artificial means, and not forced from
her ordinary course, and with high respect for the opinions of
others we must take her suggestions from the present, rather
than a very remote past period of time.

Although the Main Channel through the Lake may have once
been in the direction of the New cut, yet the interposition by
nature herself of the extensive St. Francis bank has for an indef-
inite period effectually and permanently modified her own work,
and produced the present Old Channel, which we think may now
be justly called the Natural Channel, it being the deepest, most
central through the Lake, and '-awing without artificial assist-
ance vastly the larger portion of all the waters of the St.
Lawrence River.

';'?

Again, the risk of vessels coming in collision at the curves of
the Old Channel, or within the New Channel, in consequence of
its straightness, seems to us to have been unreasonably magni-
fied.

No Channel can be safely navigated without care, and we
know from daily experience that where accidents are most
apprehended, they least often occur. It is clear also, that great
width of Channel, with moderate crooks, is better, the depth
being the same; than a straight and narrow one, as in the pre-
sent instance. But any improved Channel, however narrow or
crooked (tar more so than either of these,) may be rendered safe
by such regulations as may be established by the constituted
authorities — in illustration of which, the River Clyde in Scot-
land, furnishes a prominent example. Furthermore, the adop-
tion and perfection of the New Channel involves the stoppage of
the old one, and thereby, will force the whole trade of the River
through the New Channel, thus rendering its enlargement at
once to a width of 100 fathoms, absolutely necessary, while the
character of the entire bottom of the Old Channel, shewn by
Mr. Logan to be lime clay, easily removed by harrowing, relieves
that Channel from the difiiculties stated, as apprehended by Mr.
Killaly from the entanglement of the passing vessels with the
buoys, boats and rigging employed on the work. Nine tenths,
however, of the bottom of the New Channel, is of the same ma-
terial as that of the old, and as easily removed by similar means,
while the cut through the St. Francis bank, is chiefly coarse and
fine sand, which must be taken out by dredging. When thus fully
excavated throughout to 100 fathoms in width, and the principal
part of the St. Lawrence waters turned therein, the New Chan-
nel would doubtless have a slightly stronger current, and b3
more acceptable to all concerned than the old one. But the
above considerations viewed in connection with the estimates
will shew if the advantages of straightness, and consequent re-
duced length will compensate for the greater cost — for from our
premises it follows that this difference of cost may be so great
as to more than counterbalance the slight curves of the Old
Channel. The results of these estimates are as follows in tabu-
lar statement: • •

■■I

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t-H CC ■«'

_: 00 o
^ 1—1

«• 12

<£)

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13
in

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-a

These results s^^ow that at 13 feet depth of channel and of
the respective widths of 150, 300, 450 feet, the differences in
favor of the Old Channel are £3,935 14 4, £10,204 12 2, and
£16,685 3 7. At 14 feet depth £5,087 12 3, £20,180 18 4,
and £3^,934, 15 1. At 15 feet depth, £14, 356 8 6, £33,625
9 1, and £49,750, 8 9. And at 16 feet depth, £19,697 4 6,
£38,580 18 5, and £58,812 1 1. Or the cost by the Old Chan-
nel at 16 feet in depth and 300 feet in width is but £1,722 10 6
more than by the New of hall that width; and at the same dnpth
and a width of 450 feet the cost of the New, (£123,852 8 I,)
would be double that by the <.»ld, (£65,040, 7, 0. In fact any
available amount of money will furnish more improved accom-
modation by the Old than by the New Channel.

Viewing therefore in any aspect of width and depth, we think
that the greatly diminished cost of improving the Old Channel
more than compensates for its few curves and slightly increased
distance.

There are two other considerations worthy of note, one is,
that in addition to the diminished cost, a greater volume of water
can be diverted into the Old than into the New Channel, and with
a far less risk to the stability of the works required to be con-
structed for that 'purpose.

2nd. — It has not heretofore been contemplated to dispense
with the Old Channel, on the contrary, at the greatest width here-
tofore proposed for the New Channel, to wit, 300 feet, " that
breadth being sufficient for the special and principal purpose of
"enabling ships of heavy draft in tow of steamers to pass the
** Lake." Rafts are to be forbidden its use, " lest they should
" injure the buoys, or get in the way of vessels," neither is it to
be used by night, " the present ship Channel remaining sufficient
for the general purposes of trade."

If then as we have asserted, as much water|as can be practical-
ly and with ease accumulated should be thrown into one Channel,
and hence the propriety of closing the other; and 300 feet width
be not sufficient for the general purposes of the vast trade des-
tined to seek the St. Lawrence as its favored avenue, it follows
that a wider Channel is advisable; and we on mature deliberation
recommend 450 feet as the proper width of the contemplated
Channel to be excavated to the depth of 16 feet.

Such dimensions naturally point to the Old Channel, which for
a distance of about five miles, presents a superabundant width
and depth of water, and for the remainder of its extent is as
easily to be widened and deepened as the corresponding part of
the New Channel; and for this and other reasons stated, we are
of opinion that you should adopt the Old Channel for im-
provement and shut up and abandon the New. We cannot per*
ceive any cogency in the argument that more money should be
spent to attain an object for which much has already been inef-
fectually expended, when, as in the present instance, a less sum
applied in another direction will attain that object.

We estimate that three steamers of ) 50 horse power each, with
properly constructed harrows as large and heavy as can be drawn
five to six miles the hour will produce 13 feet depth of water in
the Old Channel 450 feet wide, throughout, in one season's work,
from the opening to the close of navigation, — also that 14 feet
depth will require the same power two seasons; 15 feet depth
three seasons, and 1 6 feet depth from years.

The same ultimate effect could not be produced in the New
Channel in a less period than six years. —

The improvements of the navigation below Lake St. Peter,
namely, on the Poulier and English Bars require for the present
in our opinions no further expenditure than the placing of buoys
designating the position of the Bars, but it may be advisable at
83me future period to make a wide passage through the English
Bar, which will admit of vessels taking a direct course.

At Isle Platte there are two Bars — one extending for a distance
of 343 feet— the other for a distance of 1666 feet.

The proper way of permanently improving the navigation at
those noints is to dredge a channel of six hundred feet in width
to a depth of 16 feet, the estimated cost of such a work will be
£2075.

The material to be removed on these Bars consists of soft clay
and sand, and at a short depth below the surface the clay is of
the same description as that found in Lake St. Peter, and may
be removed by Harrows.

The economy and success of hydraulic works, such as from
the subject of this investigation, especially require the superin-
tending care of a scientific and experienced Engineer, and as it

is fur cheaper in the end to employ skill already acquired, rallier
than incur the mistakes and current losses, of teaching, we re-
commend that these improvements, when resumed, be placed in
charge of a competent Civil Engineer and an experienced As-
sistant, the latter of whom shall reside constantly on the work.
Having been informed that considerable piling had been done
north of Flat Island, to divert water into the New Channel, we
were led to look into the condition of the work constructed, and
its eifect upon the current, but found that nearly the whole had
been destroyed — probably by the ice; we therefore present the
annexed section and plan of a Piled Dam, such as we believe
will be both cheap and durable.

The Piles being deeply driven into the bottom of the Channel,
and sunk at least two feef. under the surface of low water, and
supported by banks of enrth and stone, (as represented in the
section,) thereby giving the ice room to form, and pass over the
Dam.

In conclusion, although it does not come within our province
as Engineers, yet we cannot, in connection with the subject, but
naturally advert to the immense and growing interests to be
accommodated and promoted by any and every improvement of
the St. Lawrence, nor do we know of any more important than
that which you now contemplate.

The St. Lawrence — the natural outlet of the great Lakes—
and they connected by Railroads and Canals with the Ohio and
the " Mother of "Waters, the Mississippi," the great, the " far
West," is 'directly and largely interested in its unobstructed
navigation, and to an extent that must insure, at an early period,
its safe, unobstructed and free passage.

To this condition it will, ere long, come, for it does not con-
sist with right or reason, or the enlightened spirit of the age,
that obstacles be permitted to exist against the will and interests
of the Commercial world.

We have the honor,

Gentlemen,
With the highest respect, to remain,
Your obedient servants,

Wm. Gibbs Macneil.

' . . - ; John Child.

S. otZOWKSI.

Copy,

Steamer " RiOttfiLifcu," St. LAWHiiNOB tLivv%,
October 21 fit, 1850.
To W. E. Logan, Esq., F. G. S., Provincial Geologist.

Sir, — Having accompanied us during the past week in our
examination of Lake St. Peter, for the purpose of determining
the best mode of deepening the Ship Channel through said
Lake, and having witnessed the measurements, water soundings
and bottom borings in the two principal channels and elsewhere,
we shall now be glad to receive from you,in writing, such infor-
mation as you can readily give on the following points.

1st. The analyses of the following specimens obtained, namely,
one from Isle Platte, and two from the New Channel, being one
from the heed, and one from a mile above lower end ; three
from the Old Channel, namely, from Upper Bar, Lower Light
ftnd Buoy, and one from the English Bar near Pointe du Lac

2nd. The nature or origin of the formation from which these
fipecimens have been taken.

3rd. Your opinion relative to the effect of the present or
moderately increased currents upon the materials constituting
the Flats, Bars and Channels of the Lake.
With the highest respect,
We are,
Your most obedient seryanta,

(Signed) Wm. Macnbil,
" John Child,
^ S. Gkowski,

Board of Engineers appointed by the Montreal Harbor Commi»ti<m«rt
for the examination of Lake St. Peter.

MoNtREAL, 80th October, 1890«

Gi:ntlbmbk, — In compliance with the wish eicpressed in
your communication of the 28th. instant, I beg to state the
results of such mechanical analyses as the time has permitted, 6f
the specimens to which you allude, obtained in your borings in
the bed of Lake St. Peter, and neighboring parts of the St.
Hiawrence.

li!

1. From the Bar of Isle Platte. The bottom of the
River in this part appears to consist of clay with a thin and
probably partial coating of silicious gravel occasionally mingled
with sand. The auger was with difficulty made to bore 3 feet
of the clay, and the specimen obtained gives, after drying, 3
per cent of sand, the remainder being nearly pure clay.

2. From the Upper Bar in the Old Channel. The bed of Lake
Stt Peter is here a soft, argillaceous mud, through which the
auger was pressed without difficulty to the depth of 1 2 feet.
The material is a blue nearly pure clay. The depth of water
was here 14 feet — the rate of current in miles and decimal
parts 1*51.

3. From the Lower Light Ship. The bottom in this part is
exactly the same as in the previous instance. The auger was
without exertion pressed through 14 feet, and the materia* is a
nearly pure clay. The depth of water was ISft. 2 in. the rate of
current 91m.

4. From the Lower Buoy. The bottom here much resembles
that in the las<; two instances. The weight of one man was
sufficient to press the auger through 13^ feet of the deposit, of
which the first six inches appeared to be rather tougher than
the remainder. The material in the lower part is a nearly pure
clay. A specimen taken midway between the Lower Light
Ship and the Buoy, another two miles below the Buoy, and a
third four miles further down give nearly the same results. In
the three cases the auger with little pressure sank over 13 feet
in the mud. The depth of the water at the Lower Buoy was
14 feet ; the rate of current 0-81 m.

5. From the head of the New Channel. In this place the bot-
tom consists of sand; the auger was with difficulty worked through
5| feet, the top of which holds 48 per cent of clay, the bottom
17 per cent of the same, the remainder in each case being coarse
sand. The larger quantity of argillaceous material at the top
appears to arise from the presence of a thin stratum of clay over-
laying the sand. The depth of water was 15ft. Sin. — the rate of
4iarrent l-45m.

6. From a point about a mile and a half above the lower end
of the New Channel. The bottom here is nearly the same as in the
instance of No. 4. The borer sank with little pressure through

1 1 feet. The first six inches were rather tougher than the
remainder ; they gave a clay with 8 per cent of sand ; the
remainder is a nearly pure clay. A specimen taken a little
higher up in the New Channel, and another from the lower end, give
nearly the same results. At the lower end of the New Channel
the depth of water was 14ft. 4in. — the current 0*59 m. per hour.

7. From the Upper or Poulier Bar near Points du Lac. The
bottom here consists of tough clay, through which the borer
was with difficulty worked 2^ feet. The Lower or English Bar
near Pointe du Lac has a covering of gravel on which the borer
had no effect ; but from its proximity to the Upper Bar, it
seems propable that this gravel is underlaid by a similar clay,
and that a partial coating of gravel will be found to invest the
Upper Bar. On the Poulier Bar the depth of water was 18
feet, — the rate of current 1*17 m. On the English Bar the watev
was 15^ feet — the rate of current 0*99 m.

On desiccation, the nearly pure clays (which still hold a
minute portion of fine sand not separable by any ordinary pro-
cess of washing) have the aspect of pottery clay, or fuller's earth,
and when rubbed with the nail or cut with a knife show a glossy
surface, unctuous to the touch. In the deposits they are in a
condition of very minute division ; in those instances in which
the auger sank with facility to the various depths mentioned,
there is of course a large portion of water associated with the
clays. In this state they are by agitation readily mingled with an
increased amount of the liquid ; and on experiment an ounce of
the clay, thus mixed with about thirty times its bulk of water, and
left to subside in a vessel in which the mixture occupied a
height of 8 inches, (and in which the clay, if pressed into a solid
mass, would not present a thickness of more than a quarter of
an inch,) after resting twenty four hours, still remains suspended
to the height of three inches in so very light and fiocculent a con-
dition, with two and a half inches of opaque, turbid water over
it, and half an inch of clearer liquid above, that the most gentle
current would be sufiicient to float it away.

The argillaceous deposits of the Lake, notwithstanding their
softness, are in most places, and in the New Channel more than
in the Old, covered with a skin holding a small and varying
amount of sand which gives it a sufficient degree of tenacity to*

l-\

resist the wear of the present currents, and it seems to mo proba-
ble that once brought to a quiescent state, and thus protected, the
deposits would resist even moderately increased currents, where
the bottom is free from abrupt inequalities of surface in their direc-
tion, but that the skin broken and the deposits hj any means dis-
turbed and agitated, so as to bring them into suspension, such cur-
rents would be suificient to carry the great bulk of the material to
considerable distances. According to the best authorities, a
velocity of three inches per second or 900 feet per hour at the
botknn will just begin to work upon fine clay fit for pottery,
andhoweverfirm and compact it may be, it will eat away the surface;
yet no beds are more stable than those clays when the velocities
do not exceed the rate indicated, for the water soon takes away
the impalpable particles of the superficial clay, leaving the par-
ticles of fine sand, usually associated with it, sticking by their low-
er half in the rest of the clay, which they now protect, making a
very permanent bottom, if the stream does not bring down gra-
Tel or coarse sand, which will rub off this very thin crust
and allow another layer to be worn away. A velocity
of six inches per second will lift fine sand ; eight inches
will carry off sand as coarse as linseed ; twelve inches will dis-
place fine gravel, and twenty four will roll along rounded peb-
bles, of an inch diameter; to carry away angular fragments of
stone as large as a hen's egg requires a rate of three feet per se-
cond.

With the exception of the various Islands and their reed-
producing prolongations, constituting the delta at the head of the
Lake, several of which appear to be composed of sand, it is
very probable nearly the whole bed of the Lake will be found
to consist of the soft argillaceous mud which has been described.
In some of the borings in this, fragments of one or two species
of shells, at present inhabiting the river, were met with near
the surface, and at depths of seven and eight feet, shewing
that the deposit is the drift of the river. The argillaceous mud
was met with also in some of the numerous Channels which
intersect the sandy Islands, leading to the inference, which,
however, requires confirmation, that the clay may extend under
the sand. Fragments of river shells were found associated with
the sand also, so that whether it be over or under the clay, it is

alluvial; and it would thus appear thut no partd of tho depositH
of Luke St. Petor and its Islands are thu remains iu situ of
those clays and sands of ancient marine origin, which form a
large portion of the immediate valley of the St. Lawrence, ond
through which the main river, and many uf its tributaries have
cut their way for considerable distances. It is from the ruins of
these marine beds however ofthe post tertiary period, brought down
by the tributaries and the main river, thut the alluvial deposits
of the Lake are supplied. To pursue the material carried from
each or any individual tributary, and point out its distribution,
and the effect it may have on the waters of the main stream,
would require a much more extended investigation than the
present; but it does not appear to me to follow as a matter of
course, that because a deposit is near the mouth of a tributary, it
is of necessity derived from it. To ascertain, for example,
whether the material of the sand bank out in front of the
mouths of the Rivers Yumaska and St. Francis, is supplied by
them, would require an examination into the nature and
quantity of the sediment brought by them during freshets,
and under other circumstances; and the force and direction
of the currents then, and at other times prevailing. This
bank is a subaqueous continuation of Monk Island, the
whole of which Island is above the mouths of those streams,
and cannot therefore be derived from them; and though it is
not an improbable supposition that they may have contributed
to the material of the subaqueous part, it is not impossible, also,
that it may be due to a continuation of the supply, which formed
the Island higher up. But whencesoever the sand is derived,
there seems little doubt that the St. Lawrence current in the
Ship Channel on the one side, and the currents of the tribu-
taries on the other, have arranged and modified the form of the
bank, and that this has reacted on the currents. It is probable
that what is called the Ship Channel once ran from Monk Island
straight through the Lake, as it appears from Bayfield's sound-
ings in 1831 there were then traces of it lower down ; but the
transverse action of the tributaries has so modified the distribu-
tion of the material as to produce a deflection of the St. Law-
rence current in the Channel in question, and carry it into what
is called the Old Channel.

In respect to the soft argillaceous deposits, all the rates of
current ascertained being greater than that sufficient to give to
the bottom current the velocity required to remove fine clay, it
may be asked by what cause such a retardation of the rate has
at any time been cflfectud, as to permit the clay to come to a
state of rest. According to what has been stated, the clay
would fall at any velocity under three inches per second ; this
is understood to be French measure. A bottom current of 3
inches per second would represent a surface velocity of 7*463
inches French-per second, or expressed in English miles and de*
cimal parts, 0*47 per hour. The lowest rate of current ascertained
was 0.54 at a mile and a half above the lower end of the New Chan-
nel. But in the Old Channel, midway between the Lower Ligtii
and Buoy, two trials were made in one spot on different days. In
the first instance the rate was 0.67, and we were informed by
the light-man that the water was at the time six inches higher
than it had been some hours before, in consequence of the effect
of tide. In the second instance, the rate was 0*73, when we
were informed it was low water, the light-man's guage shewing
six inches less than on the previous trial. That the lower rate
with the higher water was a tidal result, is evident from the
fact that if the water had risen from increased supply, the current
should rather have been stronger than weaker, unless the Chan-
nel at the entrance could not carry off* the increased supply so fast
as the Channels at the head gave it, which does not appear pro-
bable. If 0*70 be taken as the current w'uen the slope of the
river is unaffected by the tide, the retardation produced by an
ordinary tide would appear to be between 4 and 5 per cent.,
and perhaps it is not assuming too much to suppose that some
occasional combinations of tidal and fluviatile conditions, such
as extraordinary high tides, and general low water in the river,
with the temporary influence of wind, may effect a retardation
of a quarter of a mile per hour, which is about the amount that
is required.

I have the honor to be.

With much respect.

Your most obedient Servant,

(Signed,) W. £. Loqan.

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