Admiral Davis’s Report—Table of the Tunnels of the
different Isthmean Routes—Altitude of Ridge at
Darien—Comparative Cost of Canals with and without
Tunnels—Lift Locks and Thorough Cut—Tide in the Atlantic
and Pacific—Moderate Lockage can not Obstruct the
Navigation—Gisborne on Thorough Cut—His Error as to
Velocity of Water—Objections to Strait—Tabular Statement
of the Cost of Tunnels, English, French, German, and
American—Tunnel of Mont Cenis—Hoosac Tunnel—Profiles
of Mont Cenis and Hoosac Tunnels—Dimensions of Ship
Tunnel—Cost of Open Canal—General Michler’s Report—Guard
Locks Necessary—Cost of System of Lift Locks—Conclusions
Supported by Garella and Michel Chevalier.
In compliance with a resolution of the Senate, dated March 19, 1866,
we have an admirable report from Admiral Davis. In this report the
relative merit of different lines is exhibited; carefully prepared
tables, showing the amount of freight which would pass the Isthmus; a
list of ninety publications and fourteen maps, are appended. Ten of
these maps, based on recent surveys, supply much valuable information.
“It is to the Isthmus of Darien,” says Admiral Davis, “that we must
look for a solution of the question of an interoceanic ship canal.” And
he quotes from Airian, “who has made a careful study of this subject,”
the assertion that, “with regard to the Cordillera, in proportion as it
advances, proceeding from the base of the Isthmus, it descends a good
deal, and is only, so to speak, a range of hills or isolated peaks, the
bases of which are intersected by ravines, which point out to engineers
the true route of the canal. The Indians in the neighborhood of
Caledonia Bay make use of these passages. One of them is elevated fifty
metres (164 feet), and is covered with a luxuriant growth of mahogany,
palm, ebony, and other trees.” “This description,” Admiral Davis
remarks, “is not based on actual measurement, but from probabilities
deduced from M. Garella’s survey of another part of the Isthmus, and
from data, equally conjectural, drawn from the published statements of
Messrs. Cullen and Gisborne.”
A thorough exploration may justify this conjecture, but no data
exists for fixing the absolute altitude at 164 feet. The value of the
statements of Messrs. Cullen and Gisborne may be contested.
It will be seen from the altitude given in the table below, that
however correct in point of fact these opinions may be, they are not
sustained by the figures taken from the maps accompanying the Admiral’s
report:
_Table showing the length of Railroads and Canals,
length of Tunnels, altitudes of Summits, estimated
cost of some of the lines proposed for uniting the
two Oceans, from actual surveys_:
═══════════════════════╤═══════╤════════════╤════════╤═════════
│ │ LENGTH │ LENGTH │ALTITUDES
ROUTES. │LENGTH.│ TO BE │ OF │ OF
│ │CONSTRUCTED.│TUNNELS.│ SUMMIT.
───────────────────────┼───────┼────────────┼────────┼─────────
│ MILES │ MILES │ MILES │ FEET
Tehuantepec │ 190 │ │ │ 855
“ │ │ │ │ 843
Honduras │ 234 │ 234 │ │ 2956
Nicaragua to Realijo │ 298 │ 160 │ │ 174
“ “ Brito │ 194 │ │ │ 600
Panama │ 53⅔ │ │ 3.7 │ 459
“ │ 48 │ 48 │ │ 280
San Blas │ 30 │ │ 7 │ 1500
Darien to San Miguel │ 42 │ │ 7 to 8 │ 980
“ “ │ │ │ │ 1020
“ Lara to Sucubti │ │ │ │ 610?
Atrato to Humboldt Bay │ 126 │ │ 3½ │
“ “ “ │ 149⅔ │ 52⅔ │ 2½ │ 970
“ to Cupica │ │ │ │
───────────────────────┼───────┴────┬───────┴─┬──────┴─────────────
│ │ CANAL │ AUTHORITIES
ROUTES. │ ESTIMATED │ OR │ AND
│ COST. │RAILROAD.│ REMARKS.
───────────────────────┼────────────┼─────────┼────────────────────
Tehuantepec │$ 16,900,000│ Canal. │ M. Moro.
“ │ 7,847,896│Railroad.│ J. J. Williams.
Honduras │ │ Canal. │ Trautwine.
Nicaragua to Realijo │ 20,000,000│ “ │ Napoleon III.
“ “ Brito │ 32,000,000│ “ │ O. W. Childs.
Panama │ 27,000,000│ “ │ M. N. Garella.
“ │ 50,000,000│ “ │ Col. G. W. Hughes.
San Blas │ │ “ │ McDougal.
Darien to San Miguel │ 65,000,000│ “ │ Gisborne.
“ “ │ │ “ │ Prevost & Strain.
“ Lara to Sucubti │ │ “ │ Bourdial.
Atrato to Humboldt Bay │ 145,000,000│ “ │ Kennish.
“ “ “ │ 134,450,154│ “ │ Lt. Michler, U.S.A.
“ to Cupica │ 325,000,000│ “ │ Trautwine.
───────────────────────┴────────────┴─────────┴────────────────────
From the above table it would appear that the altitude of the dividing
ridge falls off toward the two extremities of the Isthmus, viz.: near
the Tehuantepec and the Atrato routes, but the greatest depressions
have been found between Aspinwall and Panama, and on the line by the
way of Lake Nicaragua and Lake Managua.
At the Isthmus of Darien _altitudes of from one to two thousand
feet_ are found. Cullen’s pass of 150 feet proved to be estimated at
one-ninth of its true height. The least elevation of the divide is that
given by M. Bourdial. This engineer did not cross the Isthmus, and his
statement is so vague, the reader is left in doubt whether he actually
reached the summit. Notwithstanding this uncertainty, there still
exists a faint hope that “it is to the Isthmus of Darien we must first
look for a solution of the question of an interoceanic canal.”
From another statement in this very valuable report, we feel
reluctantly compelled to dissent. By imposing unnecessary conditions
in the statement of the problem, its solution may be indefinitely
postponed.
“The interoceanic canal,” it is affirmed, “in width, depth, in supply
of water, in good anchorage and secure harbors at both ends, and in
absolute freedom from obstruction by lifting-locks, or otherwise, must
possess, as nearly as possible, the character of a strait.”
To insist that the canal must possess the character of a strait, may
give rise to the necessity for a thorough-cut of such extreme depth,
or a tunnel of so great length, as to render the work practically
impossible. A line suitable for a thorough-cut may possibly be found,
but so important a project should not be endangered by limiting its
practicability to a communication of that nature.
If, by the employment of “lift-locks,” the cost of the canal can be
materially reduced, the question to be considered is, to what extent
such structures would obstruct navigation? This question depends upon
the amount of trade drawn to the Isthmus by the canal.
The relative cost of the two methods for piercing the Isthmus can be
best determined by a comparison of the cost of a canal in an open
country with one by means of tunnels. These considerations, since
they afford criteria for judging of the merits of different routes,
may be considered more minutely. Let us assume the trade passing over
the Isthmus—were the canal now completed—to increase one hundred
per cent. in ten years; there would then be 2,066 tons in transitu
daily, requiring seven ships of about 300 tons burthen each.[5] The
progressive increase in the size of ships will raise this average to
between 500 to 1,000 tons; reducing the number of ships arriving at
the Isthmus daily, to five and three respectively. But, assuming the
smaller average, giving the larger number of seven ships daily passing
through the canal; an increase of four hundred per cent. in the trade
would be equivalent to fourteen ships, or to seven ships leaving
opposite extremities of the canal, and passing each other daily upon
homeward and outward voyages.
Locks of four hundred feet long by ninety feet wide can be filled or
emptied in twenty minutes; and this time can be reduced for smaller
vessels by additional lock-gates, and for larger vessels by an increase
in the size and number of filling valves.
The entire trade likely to seek this route, increased four hundred
per cent. of its present amount, could be passed through one lock in
about four hours and forty minutes. As the vessels come from opposite
directions, one-half of the number would be waiting for lockage at the
same point, which would reduce the time required for this purpose to
two hours and twenty minutes. Eight locks, having an average lift of
twelve and one-half feet, would delay the increased commerce eighteen
hours and forty minutes, and would raise the level of the canal fifty
feet; while to raise the level one hundred feet the delay would not
exceed two days.[6]
As a summit level may be a necessary part of any Isthmean canal, it
is manifest that the resulting lockage can not seriously obstruct
navigation. The design of an artificial strait may therefore be
reasonably abandoned, if, by so doing, the extraordinary cost of
tunneling is excluded by the employment of a small number of lift-locks.
On account of the rise of the tide on the Pacific coast guard locks,
not much less costly than lift-locks, must be an essential part of any
canal from ocean to ocean.
The mean tide of the two oceans is about the same.
_Table of tides, according to observation, from Col. Totten’s Report._
═══════════════════════════╤════════════╤═════════════╤═════════════
│ PACIFIC AT │ PACIFIC AT │ ATLANTIC AT
│ PANAMA. │ PANAMA. │ ASPINWALL.
───────────────────────────┼────────────┼─────────────┼─────────────
│ MAY & JUNE │ NOV. & DEC. │ AUG. & SEPT.
│ FEET. │ FEET. │ FEET.
Greatest rise of tide │ 17.72 │ 21.30 │ 1.60
Least rise of tide │ 7.94 │ 9.70 │ 0.62
Average │ 12.08 │ 14.10 │ 1.16
Mean tide of Pacific above │ │ │
mean tide of Atlantic │ 0.759 │ 0.14 │ ——
───────────────────────────┴────────────┴─────────────┴─────────────
Mr. Lloyd found a difference of 27.44 feet between high and low water
at Panama. The Red Sea is 3 inches higher than the Mediterranean.
The Atlantic at Brest is 3½ feet higher than the Mediterranean at
Marseilles.
The small variation in the mean tide at Panama of the two oceans is
probably due to the action of winds and the Gulf Stream. At Panama the
highest flood tide rises about ten and one-half feet above the level
of the mean tide of the Atlantic, and the extreme ebb falls about the
same number of feet below it. The alternate currents through the new
strait, caused by the rise and fall of the tide, would prove a serious
inconvenience to navigation.
The Pacific tide, piling up at the head of the new cut, and entering
the strait with considerable violence, would be propelled toward the
Gulf in a manner analogous to the progression of the tidal wave in
a river. Upon the ebb of the tide a reverse current would prevail.
Navigation would not only be obstructed by these alternate currents,
but the channel would be choked by drifting timber washed into the
canal during the rainy season. Silt and sand would be deposited in bars
at the outlet of the canal, or swept inward to form shoals where the
current could no longer transport it.
Mr. Gisborne, in his report, devotes some space to speculations on
these results. “There can be no doubt,” he remarks, “that at high water
there will be a current from the Pacific to the Atlantic, and that
during the ebb tide there will be a current in the opposite direction.
The extent of these currents, and the place of their greatest effect,
depends on the comparative sectional area of different portions; and if
the cross-section is uniform throughout, will be some time after high
tide in the Pacific and at the Atlantic end of the canal. The phase of
the tide wave (or the appreciable effect of the tide) will take one
and one-half hours to reach from one end to the other, and presuming
the current to be uniform in the whole length”——“the question may be
examined as a maximum, _i. e._, what will be the surface velocity of
a canal thirty miles long, having a fall of eleven feet, or with a
horizontal bottom having at one end twenty-eight feet, and at the other
thirty-nine?”
Employing Du Buat’s formula, with the following quantities:
Mean depth 35.50 feet.
Mean width 183.50 “
Mean border 244.80 “
Area water section 6,147.255 “
Hydraulic mean depth 25.11 “
Fall per mile 0.33 “
he deduces a maximum surface velocity of three miles per hour. The
assumed average fall per mile is strictly a variable function, and at
its maximum would give a result greatly in excess of that deduced by
Mr. Gisborne.
There is no reason for this assumption of a fall of 0.33 of a foot per
mile. It directly involves the question to be determined, since the
velocity depends upon the inclination of the surface. The value deduced
by the formula is not the maximum but the minimum velocity attained in
the canal upon the assumed fall per mile.
There is another error in Mr. Gisborne’s statement. “The tide,” he
remarks, “would take one and one-half hours to reach from one end to
the other, presuming the current to be uniform; what,” he asks, “will
be the surface velocity in a canal thirty miles long?”
This statement contradicts his calculations, and involves also the
question at issue. If the tide travels to the end of a canal thirty
miles long in “one and one-half hours,” it is evident that it must move
at the rate of twenty miles per hour, a velocity which renders Mr.
Gisborne’s strait impracticable for navigation.
In fact, neither assumption is tenable. The problem is very complex,
or, rather, with the data given, indeterminate. It is well known that
the tide is propagated up the channel of a river in a succession
of long waves, or swells, and that when the tidal wave is entering
the mouth of the river, the waves which have reached the head are
returning. The same movement is observed, on an exaggerated scale,
in the successive breakers which roll in to meet the one which is
returning, after it has expended its force upon the beach.
In the case of the Isthmean Canal, the rising tide, after having
passed the mean, will have a downward slope into the canal. In rivers,
notwithstanding the local rise of the water, the slope is never
reversed, but is simply reduced in its angle of inclination.
The problem involves the inclination of the surface, or the
determination of the limits of tidal action at successive stages of
the tide. While the head of water increases, there is also a constant
increase of the retardation of the flow of water into the canal. The
outflowing water will run more rapidly than the inflowing, on account
of the indefinite area over which it will spread and the diminution of
the retarding influences. Both outflowing and inflowing current will
seriously obstruct navigation. The banks of the canal will wash away,
and bars will accumulate about the mouth.
While these objections are valid against a thorough-cut canal without
locks, they do not apply to a strait of a quarter of a mile in width.
As the cost of a canal is the chief difficulty in the way of its
construction, it is necessary to abandon the idea of a strait, and to
adopt that of a thorough-cut with guard-locks, as the only known means
of protecting the canal from the injurious effects of the tide.
In order to form a correct opinion of the cost of canals with and
without tunnels, attention is called to the expense incurred in the
execution of this kind of work.
_Dimensions and Cost of some English Tunnels._
══╤═══════════════════════╤═══════╤══════╤═════════╤══════╤════════
│ │ │ │THICKNESS│LENGTH│KIND OF
│ │HEIGHT.│WIDTH.│ OF │ IN │MASONRY.
│ │ │ │ ARCHING.│YARDS.│
──┼───────────────────────┼───────┼──────┼─────────┼──────┼────────
│ │FT.IN. │FT.IN.│ FT.IN. │ │
1 │Thames & Med. Canal │ 39.0 │35.6 │ ... │ 3960 │ BR’K
2 │Islington, Regents Can.│ 21.6 │20.6 │ 1.6 │ 900 │ “
3 │Tetney, Haven Canal │ 16.2 │17.0 │ 1.2 │ 2962½│ “
4 │Walford, N.W.R.R. │ 26.6 │27.0 │ 1.6 │ 1830 │ “
5 │Box Tunnel, G.W. “ │ 36.0 │36.0 │ 2.3 │ 3121 │ “
6 │Littleboro’, M.&L. “ │ 27.6 │27.0 │ 1.10½ │ 2860 │ “
7 │Thames, Foot Passage │ 2.3 │37.6 │ 2.6 │ 400 │ “
8 │Bletchingly, S.E.R.R. │ 30.0 │30.0 │ 1.10½ │ 1324 │ “
9 │Saltwood, “ “ │ 30.6 │30.0 │ 2.3 │ 954 │ “
──┼───────────────────────┼───────┴─┬────┴───┬─────┼──────┴────────
│ │ TOTAL │COST PER│YEAR │ MATERIAL
│ │ COST. │ YARD. │WHEN │ CUT THROUGH.
│ │ │ │BUILT│
──┼───────────────────────┼─────────┼────────┼─────┼────────────────
│ │ DOLLARS.│ DOLLS. │ │
1 │Thames & Med. Canal │ ... │ 145.00│1800 │Chalk,
│ │ │ │ │ Fuller’s earth.
2 │Islington, Regents Can.│ ... │ ... │1812 │London clay.
3 │Tetney, Haven Canal │ 563,405│ 192.50│1827 │Various.
4 │Walford, N.W.R.R. │ ... │ ... │1838 │Chalk.
5 │Box Tunnel, G.W. “ │1,561,500│ 500.00│1838 │Freestone.
6 │Littleboro’, M.&L. “ │4,255,000│ 440.00│1841 │Various.
7 │Thames, Foot Passage │2,273,570│5,685.00│1842 │London clay.
8 │Bletchingly, S.E.R.R. │ 486,185│ 351.00│1842 │Shale.
9 │Saltwood, “ “ │ 562,710│ 590.00│1843 │Lower greensand.
──┴───────────────────────┴─────────┴────────┴─────┴────────────────
Canal tunnels are rarely larger than 16½ feet by 18 feet high.
Supposing the same dimensions to obtain in French tunnels, the cost per
lineal yard of the following named tunnels will furnish a basis for
comparison:
═════════════════════════════╤═══════════╤═════════
│ LENGTH │ COST PER
NAMES OF TUNNELS. │ IN YARDS. │ YARD.
─────────────────────────────┼───────────┼─────────
Norieu, St. Quinten Canal │ 13,128 │ $14.00
Pouilly, Canal de Bourgoyne │ 3,660 │ 393.75
Soussay, Canal de Bourgoyne │ 3,852 │ 45.50
Maurages, Canal de Marne │ 5,320 │ 325.00
St. Argnan, Canal d’Ardennes │ 288 │ 200.00
─────────────────────────────┴───────────┴─────────
[Illustration: PLAN AND PROFILE OF MONT CENIS TUNNEL]
Among railroad tunnels, the following are selected from different parts
of the continent:
════════════╤═════════╤═══════╤═══════╤═════════╤═════════
NAMES OF │ │ │ HEIGHT│ NUMBER │ SECTION
TUNNELS. │ LENGTH. │ WIDTH.│ ABOVE │ OF │ ABOVE
│ │ │ RAILS.│ SHAFTS. │ RAILS.
────────────┼─────────┼───────┼───────┼─────────┼─────────
│ YDS. │ FT. │ FT. │ │ SQ. FT.
Chezy │ 496 │ 24.27 │ 18.04 │ 0 │ 365.84
Arschwiller │ 2928 │ 24.27 │ 18.04 │ 6 │ 374.77
Alouette │ 1350 │ 25.58 │ 20.00 │ 21 │ 428.68
La Motte │ 2799 │ 24.92 │ 21.98 │ ... │ 519.71
Nerthe │ 5072 │ 26.24 │ 24.60 │ 24 │ ...
St. Martin │ 1509 │ 25.25 │ 19.35 │ 10 │ 415.34
Blaisy │ 4483 │ 26.24 │ 24.60 │ 20 │ ...
────────────┼─────────┼───────┴───────┼─────────┴─────────
NAMES OF │COST PER │ TIME IN │
TUNNELS. │RUNNING │ CONSTRUCTION. │ MATERIAL.
│ YARD. │ │
────────────┼─────────┼───────────────┼───────────────────────
│ DOLS. │ MO’S. │
Chezy │ 411 │ 32 │ Sand and clay.
Arschwiller │ 176 │ 95 │ Sandstone.
Alouette │ 305 │ 23 │ Clay.
La Motte │ 180 │ 30 │ Clay, marl, sandstone.
Nerthe │ 412 │ 36 │ Limestone.
St. Martin │ 475 │ 60 │ Porphyritic rock.
Blaisy │ ... │ ... │ Limestone.
────────────┴─────────┴───────────────┴───────────────────────
The cost of the Thames tunnel was greatly increased by a shield,
designed by Brunel, to keep out the water. Omitting this tunnel from
comparison the English works exceed the French, or Continental, in cost
of construction.
The boldest work of the kind yet undertaken is the Mt. Cenis tunnel, to
connect France and Italy by a continuous railway. In length it is seven
miles, with a width of 26′ 6″ and a height of 20′ 8″. Its completion is
anticipated in April, 1871.
The monthly advance by hand-labor was twenty-two and a-half yards. The
progress is doubled by machinery, and during the past year has averaged
330 feet per month. Air, compressed by water power, is conveyed
inside to give motion to chisels, which form cavities for blasting by
gunpowder. The average progress per day in 1865, with the machinery,
was about 9 feet.
The estimated cost was $550 per running foot, but the rate was
increased to $640; the entire cost of the tunnel being estimated at
$9,200,000. The use of machinery at Mt. Cenis was found to expedite the
work, but at an increase of expense.
The trial of machinery at the Hoosac tunnel, upon the Troy and
Greenfield Railroad, has not been favorable to its employment. This
tunnel will be four and three-quarter miles long. Originally projected
with a width of 24 feet, and a height of 20 feet, it has been
contracted to 14 feet wide, and 18 feet high. The estimated cost was
$2,696,229. The rate first assumed was $137 per running foot. The rate
per cubic yard varies from $5 to $22, and $30, for the excavation of
shafts.
The contract prices for the Hoosac tunnel, in 1869, were as follows:
Tunnel enlargement, per yard $ 16.00
Heading enlargement, east end, per yard 9.00
Heading enlargement, west end, per yard 9.75
Full size tunnel extension, east end, per yard 11.00
“ “ west end, per yard 12.00
“ “ central section, per yard 14.00
Central drain, with air and water pipes complete,
per lineal foot 13.00
Sinking shaft (27 × 15), per foot, depth 395.00
Pipes (10 inch), set in shaft 6.00
Arching (in brick at $9 per M), per M 22.00
Excavating and constructing 50 lineal feet of stone
arch, and filling 23,000.00
Although more than two hundred railroad tunnels have been constructed
in the United States, and an unknown number of canal tunnels, facts in
regard to them are difficult of access. Recent bids for tunnel work
upon United States railroads have been offered at $5.40 per cubic yard
for excavations. Canal tunnels, of the ordinary dimensions of 297
square feet area, would cost $113.20 per running foot.
The uncertainty of the nature of tunnel excavation, the unexpected
difficulties to be overcome, baffle all anticipatory estimate. The
variable rates in the preceding tables establish this fact. The average
cost per running yard upon French canals is about $152, which sum
probably includes arching. Rates of labor in the United States would
increase the cost about four times this amount.
Comparing the contract price of American tunnels, as given above, with
the table of English tunnels, and bearing in mind that the cost of
arching is included in the latter, we find in Nos. 3, 6, and 9, the
cost of English tunnels is in excess; number 3 being nearly double,
and number 9 one-tenth more, while, in every other case, the cost at
American rates is greater, varying from one-third to five and one-half
times more.
The shale, schist, and trachyte of the Isthmean ridge is of variable
consistence. Many places exhibit friable, seamy strata, disintegrating
upon exposure to the atmosphere. A tunnel of the dimensions to admit
the passage of ships, when carried through rock of this character,
will require a lining of masonry to prevent falling material from
obstructing the way.
To pass ships with the topmast struck, the intrados of the arch should
be 100 feet above the surface of the water. A semi-ellipse with
semi-transverse, and conjugate diameters of 100 feet, added to the
canal prism of thirty feet in depth, will give an area of tunnel equal
to 10,104 superficial feet, or to 1,976,263 cubic yards per mile.
[Illustration: PROFILE OF THE HOOSAC TUNNEL]
Assuming that the cost of tunneling through the Isthmus can be executed
at $10 per cubic yard, we shall have 19,762,630 dollars as the cost of
one mile of tunnel. Estimating the excavation alone at present contract
price, $5.40 per cubic yard for small tunnels, one mile of ship tunnel
will cost $10,670,820. An open canal upon the line of the canal
proposed by General Michler, uniting the Atrato with Humboldt Bay, will
cost, according to the estimate of that officer, $1,792,202 per mile.
This amount, taken from the careful and elaborate estimates contained
in General Michler’s report, may be assumed as a basis of comparison of
the two proposed methods of intermarine communication, viz.: by uniting
the two oceans upon one level by a tunnel, or by means of a moderate
number of “lift-locks.” Eight locks, four at each end of the canal, or
sixteen locks, eight at each end of the canal, will raise the summit
fifty feet above tide in the first case, and one hundred in the second,
and will cost eight millions, and sixteen millions respectively. Since
two guard locks will be requisite for either method of communication
(_i. e._ by “strait,” or canal with lift-locks), their cost should
be excluded from the above sums, which are thereby reduced to six
millions, and fourteen millions of dollars. These sums are fixed as the
probable limits of the cost of a system of lift-locks sufficient to
overcome the divide of the Isthmus, and also to supply the reader with
a standard, by which he may judge of the merits of different routes.
The construction of a ship tunnel is, as has been said, “a herculean
task,” and it is not apparent that “the prejudice against it will
be removed by the operations at Mt. Cenis.” A moderate number of
lift-locks seems preferable to a tunnel of one mile in length, which,
in turn, would be more economical than an excessive number of locks. A
greater number than we have mentioned may be deemed excessive.
A thorough-cut upon the level of the ocean would be a desirable method
of canalization, but it seems like hampering the important design
of an intermarine highway for the commerce of the world, with an
impracticable condition, to insist that it should possess “absolute
freedom from obstruction by lifting locks,” or that it should possess,
in any degree, the “character of a strait.”
In this statement I find I have the support of M. Garella and Michel
Chavalier. The opposition to the system of lift-locks appears to have
originated in the objection expressed in Mr. Wheaton’s letter to Mr.
Buchanan, to the large number of these structures, recommended in M.
Moro’s plan for the canalization of the Isthmus of Tehuantepec.
FOOTNOTES:
[5] Present average of the tonnage of ships of the commercial marine
is 380 to 400 tons. The calculation supposes a commercial year of 300
days, and that the same number of ships arrive daily.
[6] The Egyptian correspondent of the Boston Advertiser, March 15,
1870, observes: “The channel at Lake Timseh has not much more than 19
feet of water, as on the day of opening. We met two steamers on their
way to Bombay, an English vessel going for cotton, and the French
steamer Asie. This was evidently all the business of the day, and from
the report of the company, it is a fair average of the amount of work
done. The company say they register one thousand five hundred tons a
day.”
In December, 1869 9 steamers and sailing ships 40,000 francs.
In January, 1870 16 “ “ 170,000 “
In February, 1870 28 “ “ 269,000 “
In March, 1870 52 “ “ 450,000 “