The Panama Canal and its Makers Part 2

[Ill.u.s.tration: LIDGERWOOD UNLOADER, WINDING APPARATUS.]

[Ill.u.s.tration: _ANOPHELES_ BRIGADE OILING A DITCH.]

Next let us see what are the special difficulties of the high-level project.

This also depends for its success mainly on the efficacy of one dam, which is now being made at Gatun. It will hold up the waters not only of the Chagres but of its tributaries, to a level of 85 feet above mean tide, and the area of the lake thus to be formed is shown on the map.

The Chagres will be ponded back far above the point where it enters the Ca.n.a.l, and thus will be effectually tamed. The flood-waters will be spread over an area of about 164 square miles--for Lake Gatun will be twice the size of Lago Maggiore and about four-fifths that of the Lake of Geneva,[9] and ships, in the ample waterway, will not be troubled by currents.

[9] The size, in fact, will not differ greatly from that of the princ.i.p.al basin of the Lake of Geneva, all above the _pet.i.t lac_, or narrow part at the Geneva end. A good idea of this area is obtained by recalling the well-known view over the waters of this lake from the _quai_ at Ouchy.

A flight of three locks at Gatun will raise ships to the level of this lake in coming from the Atlantic, and one lock at Pedro Miguel and two at Milaflores will lower them to the level of the Pacific.

It has been claimed that if the Gatun dam burst the consequences would be less disastrous than if the Gamboa dam burst, but there is in reality little to choose between the two catastrophes.

The great blot on the high-level scheme is that the great Gatun dam is not founded on solid rock. The Gamboa dam of the tide-level project would have been founded throughout on hard rock, from which it could have been built up of masonry so that the structure should be part and parcel of the rocky framework of the globe itself. The Gatun dam as recommended in the minority report, on the other hand, was designed to consist essentially of a ma.s.s of earth dumped upon an alluvial plain so as to fill up a gap of 2,000 yards between two ranges of hills, the gap through which the Chagres escapes to the Atlantic. Thus the Gatun lake was to be held up as a glacier lake is held by a moraine blocking a valley.

We shall presently describe the high-level ca.n.a.l as it is to be, from which it will be seen that it will provide a magnificent waterway, but before concluding the present section I must mention the special point in which it will be inferior to a tide-level ca.n.a.l. This is for purposes of defence. A fortress has to be preserved from capture, but not from damage. The locks, however, must be preserved from serious damage, which demands far more elaborate protection. Such protection, moreover, has to be provided at two positions (Gatun and Milaflores) about 30 miles apart.

_The High-level Ca.n.a.l as it is to be._

The Spooner Act, the law under which the Ca.n.a.l is being constructed, enacts that it shall be "of sufficient capacity and depth as shall afford convenient pa.s.sage for vessels of the largest tonnage and greatest draft now in use, and such as may reasonably be expected."

Accordingly the following dimensions have been selected:--

1. A minimum depth of 41 feet.

The Suez Ca.n.a.l has a depth of 31 feet[10] admitting of the pa.s.sage of ships with a draft of 27 feet.[11] The channel of this ca.n.a.l is now being deepened, so that by 1915 it is hoped that a depth of 36 feet[12]

will be obtained. The Kiel Ca.n.a.l has a depth of 30 feet. The average draft of the Cunard s.s. _Mauretania_, the largest ship now afloat, is about 32 feet, but she is stated to draw, when fully laden, about 37 feet, and there are comparatively few harbours in the world which she could enter fully loaded.

[10] Report, Board of Consulting Engineers, p. 175.

[11] "Four Centuries of the Panama Ca.n.a.l," p. 436.

[12] _Daily Telegraph_, June 18, 1908.

2. A minimum bottom width of 200 feet in the Culebra Cut.

The minimum bottom width, or width at a depth of 31 feet, in the Suez Ca.n.a.l is 108 feet.

The bottom width of the Kiel Ca.n.a.l is 72 feet.[13]

[13] Report, Board of Consulting Engineers, p. 173.

3. Each lock will have a usable length of 1,000 feet and a width of 110 feet.

The locks of the Kiel Ca.n.a.l have an available length of 492 feet and width of 82 feet.

The _Mauretania_ has a length of 790 feet and beam of 88 feet.

4. The minimum radius of the curves is 5,577 feet (1,700 metres).[14]

This curve, however, does not come in the Culebra Cut, where the bottom width is to be 200 feet, but north of Bas Obispo, where the bottom width is 500 feet. Most of the curves have a radius of 9,842 feet (3,000 metres).

[14] _Vide_ p. 205 of General Abbot's "Problems of the Panama Ca.n.a.l"

(1907). Slight changes in the projected course are made from time to time, so that this figure is subject to slight modification.

In the Suez Ca.n.a.l,[15] outside Lake Timsah, there are five curves with a radius of 2,000 metres, or a little more, which are being enlarged to 2,500 metres (8,202 feet). The usual bottom width in these curves was 184 feet, but this is being increased to about 230 feet. The Kiel Ca.n.a.l has four curves with a radius of 1,000 metres (3,284 feet).

[15] Report, Board of Consulting Engineers, p. 178.

A reference to the accompanying plan (_vide_ Map, end of volume) of the Panama Ca.n.a.l will show that most of the curves are situate in Gatun lake, where the width of the ca.n.a.l proper is large, and where the spread of shallower waters secures better steerage.

Thus the high-level Ca.n.a.l is not only deep and wide, but also much freer from troublesome curves than might be supposed from a casual inspection of its course. The details of the bottom width of the high-level Ca.n.a.l in its different parts are as follows:--

Feet.

From the Atlantic entrance to Juan Grande (27 miles) 1,000 Juan Grande to Bas Obispo 500 Bas Obispo to a point about half-way between Empire and Culebra 300 Culebra Cut nearly to Pedro Miguel lock (about 4 miles) 200 Pedro Miguel to Pacific entrance 500

[Ill.u.s.tration: 100-TON WRECKING CRANE, GORGONA.]

[Ill.u.s.tration: INTERIOR OF MACHINE SHOP, GORGONA.]

Limon Bay being shallow, the deep water where a battleship can freely navigate or manoeuvre lies outside a line joining Colon Lighthouse with Toro Point, and at a distance of 7-1/2 miles from Gatun locks. From this distance the lock-excavation can now be plainly discerned from the deck of a ship without the aid of a gla.s.s. Here, when the Ca.n.a.l is complete, a ship will enter the buoyed channel of the submarine portion of the Ca.n.a.l, but this part of the channel does not lead directly towards the locks, which are not visible upon the face of the water.

Moreover, they are presently hidden altogether by the land. Not until Mile 5, near Mindi, is reached does the course of the Ca.n.a.l, by a slight bend, open up the locks to uninterrupted view, and at this point the ship is already confined between banks. When the foot of the flight of three locks is reached a vessel will no longer proceed under her own steam, but be warped through.

The length and width of the locks has already been stated. The maximum lift will be 32 feet, or about 4 feet more than in any other locks at present in use. As the width (110 feet) is much greater than that of existing locks, it follows that the lock gates will be far larger than any now in use. The vessel has to pa.s.s through a flight of three succeeding locks. Parallel with this is a second flight of three locks, so that two ships could be simultaneously put through either flight in the same, or in opposite, directions. Each lock through which the vessel pa.s.ses on her upward course is provided with two pairs of mitre gates, _i.e._, double-swinging doors, but the uppermost lock has in addition a rolling gate near the lower end. This is a precaution against the breaking through of the upper folding doors by a ship coming down, _i.e._, from the Pacific side. An emergency gate is also being designed, a sort of swing bridge, to close the upper entrance to the flight of locks, for Gatun, Pedro Miguel, and Milaflores. It is hoped that a vessel will be put through all three locks at Gatun in 50 minutes, to which must be added some delay in approaching. Coming from the Atlantic the water of the Ca.n.a.l will be smooth, and the vessel somewhat sheltered, so that there should be no difficulty. Approaching from the lake there may be some roughness, but anything more than a fresh breeze is rare, and the lake will be practically free from currents, so that the approach should present little difficulty. The Pacific side is always calm, so that no difficulty of approach or exit is to be antic.i.p.ated there on account of either winds, waves, or currents.

Our vessel, having been locked up to the broad surface of Lake Gatun, proceeds under her own steam and at a fair rate of speed across that lake, slowing down to about 4-1/2 miles per hour for the 9 miles of Culebra Cut, which will thus occupy two of the 8 or 10 hours in which it is hoped to accomplish the whole transit. On this basis it is calculated that 40 ships could be put through in 24 hours from the Atlantic to the Pacific, or two fleets of 20 ships if pa.s.sing simultaneously in opposite directions.

A 10-hour transit of the 50-mile channel is about the same rate of progress as that in the Suez Ca.n.a.l, where, though there are no locks, the speed has to be kept low on account of the friable nature of the banks.

It is evident that the time of transit cannot yet be certainly known to an hour or two, but a considerable margin beyond the above estimate would enable the pa.s.sage to be made between dawn and dusk of the tropical day.

At Pedro Miguel our vessel pa.s.ses through one lock on her way down to the Pacific, and at Milaflores through two locks. Each of these three locks has, of course, a duplicate alongside, permitting, as at Gatun, the simultaneous pa.s.sage of a companion vessel, or of one pa.s.sing in the opposite direction. In case of repairs to one set of locks the parallel set would maintain the waterway.

The lift of the lower lock at Milaflores is variable, depending upon the level of the tidal water in the last reach of the Ca.n.a.l. The extreme range of the tide at La Boca, the Pacific entrance to the Ca.n.a.l, is 20 feet; that is to say, low water during "spring" tides is 10 feet below the average sea-level. During low tide on the Pacific side, therefore, the water in the Ca.n.a.l stands 95, instead of 85, feet above that sea.

Hence the maximum lift of 32 feet already stated, for

32 3 = 96.

[Ill.u.s.tration: MACHINE SHOPS, GORGONA.]

[Ill.u.s.tration: CLUB HOUSE FOR EMPLOYEES, GORGONA.]

Beyond the Milaflores locks our vessel enters a reach of the Ca.n.a.l which is exposed to the ebb and flow of the tide and _which will be confined within banks or levees as far as La Boca_. In this respect the plan and the section are both, unfortunately, misleading. The La Boca lock and dam have been abandoned, and no Sosa lake will therefore come into existence, the lowest lock being, as I have said, at Milaflores. I have thought it better to reproduce the existing maps as they stand rather than to attempt a re-draught which would necessarily be imperfect. Our vessel, then, below Milaflores is in a tidal channel and will be subject to some tidal current. By designing this channel so as to avoid a bottle neck, and by giving it a width of 500 feet, the calculated current will, however, not exceed 1 foot per second.

The La Boca site for locks was found to be much too exposed to gun fire and other modes of attack from the sea, whereas the Milaflores site is not only distant about 5 miles from the sh.o.r.e, but is well sheltered both by hills near it and by the position of the hilly eminences of the sh.o.r.e line.