THE ISTHMIAN CANAL.

Dominion, Volume 6, Issue 1634, 28 December 1912, Page 6

THE ISTHMIAN CANAL.

PANAMA VISITED. IN THE CULEBRA CUT. / ELEMENTS OP DANGER. (By G. H. Scales.) 111. (Continued.) In- The Dominion yesterday was published the first part of Article 111 of Mr. G. H. ScaJes's impressions of tho Panama Canal. Thercan, the author conveyed Ms readers over the finst two sections of the canal system—the sealevel section, and the Gatuai Lake and Dam Section—prefacing his survey with an interesting description of the look system. In tho remainder of the article, published hereunder, the famous Oulebra Out and the principal features of tho other sections of the oanal eyetern aj'e described, and the author ventures an opinion on certain clemente.of possiblo danger to the commercial success of tho undertaking.

The Culebra Cut. The third section is a length of 9} miles on the 85ft. level, and is all cutting. This is known as the Culebra Cut. Of a total estimate of 195,000,000 cubic yards to be excavated, over 85,000,000 will, on completion, have been taken, from this one section, and it is not improbable that the quantity named may be considerably exceeded. The width'at the bottom of the cut is 300 feet, but at the top there is great variation, due to the different 6oils the cut passes through. The greater part of the country is liablo to "slide" or "slip," and the original estimates have had to be enormously increased owing to the inoessant slips. The width at the top at one place is now estimated to. bo over 1800 feet, due to a huge slide, and there is no certainty thht this action of the earth has yet stopped. A cablegram appeared in a Jamaica paper only a. day or two ago (this article was written.early in October) quoting the rumour of another million yard 9 slide, and although ' this rumour had not the "offioial stamp" on it, it had an "ofßcial tag" to the effect that "small slides such ais a million yards" were not offioially reported, The waterway through this cut .will be by no means a' straight run, but the curves will be easily negotiable by -the largest vessels whilst travelling- at a slow speed. The highest point on which excavation has taken place is at Gold Hill, near the town of Culebra, over 500 feet, but this was merely "face" work. The highest point on the centre line of the canal is 312 feet above sea level, meaning an excavation of about 250 feet. The width,-as

originally planned at water level right through the cut is only slightly in excess of "bottom width," from which it will bo seen there is little or no "batter," the" 1 sides being almost perpendicular.

Formation and Slides in the "Cut." In some places, but not as a general rule, the formation of the country may warrant tliis, but as it very largely consists of loose, broken rock, alternating with patches of soft, very friable, loamy soil, and patches of a harder, yellowish cloy, ail, at times, indiscriminately juuibled up together as though hurled from the depth of somo volcano, the question arises as to what may happen when the cut is filled with water and vessels are passed through, even at a very' slow speed. Not only have vast slides from the top downwards taken place, but tho pressure of the top weight of the sides has in some places been sufficient to force the floor of tho canal up, to.bulge it out, as it were, though it is considered that as eoon as the canal is filled with water the pressure of the latter will successfully resist the pressure from tho sides. If tho theory is sound all will bo well. But if the weight of land is too much for the water—what then? Tho official reply would be, it is understood, "Excavate from the back of the slide." It sounds a large order, but compared with the whole construction i 9 only as a.molehill is to a mountain.

Silica 1905 over 9,000,000 cubic yards havo been taken out as ,tho special result of slides in several places in the "cut," and there are now somewhere in the neighbourhood of 8,000,000 cubio yards still actually in motion. There is one perpetual process of blasting going on, and as soon as in any one spot this ceas63, the steam dippers and shovels fill the iroins, which aro promptly taken off to the dump. The best day's work dono was the shifting by the dipper of about 80,000 cubic yards and tho filling and discharging of 393 trninloads. Tho average yard of spoil in the "cut" is estimated to weigh. 36001b.

Railroad Haulage. At Baa Obispo, the northern end of the "cut," a temporary dam or dyke has been put across the canal way on tho south bank of the Chagrin so k«epnig the water from entering this scction of tho canal-bed. The railway at this point crosses tho canal to Gorgona station, -lnd does not re-cro?3 until near Pnetlro Miguel, at which place it is carried over on temporary trestles about JCO feet Thoro ia on® long continued stream of ballast trains runiliß la and, out of tlio

"out," dumping their contents in various parts of the works. Two kinds of ballast trains are in use, one consisting of a low side steel wagons, the bodies supported on a oentral pivot-framo running fare and aft, and made fast by two hook chains on either side; immediately these hooks on one side are loosened the trucks auto.matically empty themselves. The other consists of one-sided low trucks on the end, one of which is placed what is called the "plough" to the- point of which is attached a wire ropo connecting with a drum carried, on the truck next the engine, and this drum, when set in motion, winds up the wire and so hauls the plough from one end of the train to the other. By covering the apace between the trucks with a sheet of iron a continuous floor is made from end to end. As soon as the empty train ib moved away two other machines are brought into operation consecutively, the "spreader and leveller," and the "track shifter." The former spreads and levels the soil deposited, whilst' the latter picks up bodily the track oh the dumping ground, and shafts it in the required direotion. The result of this combination is that in praotically a few minutes some 300 tons of spoil are not only discharged. from a train, but put in placo and finally disposed ' of. As / evidencing the amount of haulage going on in this cut, it may be mentioned that on the nine and a half miles there are 75 miles of railway track being worked, whilst, on the whole field of operations the total mileage is said to be about 500. The average depth of excavation over the nine and a half miles is about 120 feet, and in March last there remained over 13,000,000 cubio yards to be disposed of. This quantity will probably he nowhere near tho total to be shifted owing to slides., In the year 1911 about 16,000,000 cubio yards were shifted, and .therefore, if the opportunities or facilities for operation have not been curtailed proportionately to the lessening of the quantity, it is not unreasonable to suppose that by March next the excavation on the cut should be finished. ■" But slides have to ho reckoned with. The scope of the operations in the out has been materially reduced, and. has now been confined to a distance of about six miles rising from either ends towards the centre to a height of about 40 feet. Tho position, therefore, does" suggest that there may be difficulties in maintaining what has been the usual average daily output,_ _ Still, as tho hours, so far, have been limited to the ordinary eight-hour day, it may be possible to make up some leeway by an extension in the' working hours, always provided, that is, that the West Indian can respond. to the demand.

Puedro Miguel Lock. Some 40 miles of the whole urea of the canal have now been dealt with, and exoeptfor locks on the Pacific side of the divide, this' area comprises not only that on which most work has had to be done, but is, to the visitor, of the most intsr-

est. The Culebra Cut runs out,on the north, side of ivhat is known as the Puedro Miguel Lock, and leads, 1 of course, into that lock, which, with the exception that it is only a single chamber, is in all. respects similar to fctatun. It is the first step downwards from tho 85 feet level to. the Pacific sea level, and vessels passing through it are raised or lowered, as the case may ho, a distance of 30 feet. At Puedro Miguel two'dams' are in course of construction for the purposes of retaining tho waters of the Gatun Lake, which, emerging' from the Culebra Cut, will extend over a considerable area of low-lying country to the north of tho lake. These dams extend from the lock to the hills on. either side of the basin through the centre of which, it has already been explained, the canal passes. The dam to the west is of earth, and is about a quarter of a milo long, its crest being 105 fept above mean sea-level (Pacific), whilst a somewhat longer one— a concrete core wall—is carried from the lock to the eastward hills.

Mira Flores. The fourth section consists merely of about one mile and a half, and extends from Puedro Miguel lock to Mira Flores locks. This is at'present a basin at tho foot of fairly high hills on either sids>, into which the waters of one or two comparatively small rivers will be not only discharged, but confined, flooding tho whole of the basin and turning it into what is to be known as the Mira Flores lake. The width of the actual channel of the canal through this lake will be about 500 feet.

Tho Mira Flows looks consist of two flights, in other respects being exactly similar to Gatun and Puedro Miguel. These two flights will raise or lower vessels the difference, 55 feet, between tho surfaco of - the water on Mira Floras lake l'iso and fall of tho tide at Panama is riso and fal lof the tide at Panama is 20 feeh at Colon it is only 20 inches. The Mira Flores locks are comparatively close to the eastern side of the basin, and such 6j>nco as there i 3 between them and the hills is being used as a weir or spillway for the surplus waters of Mira Flores lake. On the western side a large- dam is being constructed in manner similar to that at Gatun, running north, almost parallel to t'lio canal, for tho purpose of confining tho river waters previously alluded to within the required boundaries of Mira Flores lake.

Balbao, The fifth and laat paction extends from

Mira Flores look at the southern ond of Mira Florcs lake to doop water in tlie Bay of Panama, a distance of about eight miles. Sorno considerable amount of excavation below this lock has yet to be dons, and sluicing operations with huge iets of water are in full swing, for loosmv ing the material to bo removed. As it approaches the,sea, however, more work has been done, and it gradually deepens until a mile or two away from the lock, the only sign of its being anything more than a very picturesque inlet is the buoying of the Canal Channel. This leads up to, and past, Balbao, which is the aone port at the Panama end, where large and extensive operations by way of reclamation and the construction of sheds and wliarves are in progress. There is good accommodation now for many aceati steamers but extensions are proceeding in'all directions. A largo breakwater three i£o four miles long is being stretched across the extrance of the Bay of Panama from the eastern mainland to Noas Island, which is just where the Canal Channel begins, the special object being to prevent the drifting of sand owing to the action of a current setting up the coast into the bay. As indicating what some of the unknown quantities were that had to be estimated bjr the it may bo mentioned that in the construction of this breakwater—the surface of which is 29 feet above the surface of the sea bottom—official records show that the actual quantity used was no less than ten times the quantity required theoretically.

Elemonts of Possible Danger, Whether, as a Buccessful undertaking, the Canal will be able to maintain its greatness remains to bo proved. There are not .wanting some who doubt it. But there is no room for doubt as to the existence of at least two elements of difficulty that at tiro eleventh; hour may at rate postpone the period of its recognition as an unqualified success. These. are the necessity of keeping tho land out of tho waterway, and of keeping enough water in.it. The first, and the reasons causing it have already been referred to at considerable length. The nature of the formation f:f the soil creates a risk of unknown quantity. that will not cease until not only is the canal flooded with water, but vessels have for some period successfully navigated it. There are at the present time several miles of the cut to be excavated' to the required depth, a considerable portion, as much as •40ft., and until this is completed it is difficult, even if possible to tell whether the sides will or will not slide into the bottom of the cut, or force the bottom of the cut upwards.

The second element referred to .is an even more serious possibility than the first. The whole conception of this vast undcrtakiag is based upon a sufficiency of water being available from the Chagres to give the required depth in the channel through the Gatnn Lake ' and work the locks throughout the year. For eight or nine months, during which . time

there is a heavy rainfall over the area of the water-shed, there will be more than, sufficient, but as during the rest of the year the rainfall is very small, it will be necessary to have conserved by tho end of the Tainy season a sufficient surplus to ensure the required quantity of. water for the dry months being available. There will be three causes of loss—evaporation, leakage, and use. Estimates have been made as to the quantities that may reasonably be expected to represent the mea sure of each of theso.' The last will be mainly for tho locks, and on the basis of a specific number of ships going, through in each twenty-four hours) a practically exact computation of how much water will have to be discharged as a maximum can be arrived at. This maximunl will be subject to be reduced by the sacrifice of "time in transit" owing to the arrangement by-which, when two ships are in the same lock at tho same time, and going different ways, tho water for one chamber can be used for operating its parallel, though' this might result in some detention to the vessels. There will bo a certain amount of leakage in all probability at the locks and the spillways, as • well as some due to the extremely porous uatiiro of the soil, and tho evaporation will be considerable.

Provision has been made by which ail additional two feet in the depth of tfater of the Gatun Lake may be obtained, and it is proposed that prior to the beginning of' the rainy season this nrovision shall be taken advantage of. It is confidently expected that the additional quantity will bo sufficient to meet all possible requirements. The whole proposition, however, in this particular connection is based upon estimates without, so •far as can be ascertained, the data for the eame being particularly reliable though the principal factor, i.e., tho estimated discharge of the Chagre3 Eiver into the lake is computed from figures recorded by French engineers over a period of many years. (To be continued.)