THE ISTHMIAN CANAL.

Dominion, Volume 6, Issue 1633, 27 December 1912, Page 5

THE ISTHMIAN CANAL.

PANAMA VISITED. LOGIC SYSTEM DESCRIBED. (By George H. Scales.) 111. Except in ouo particular, which will le referred to later, the whole of the locks along tho Pauama Canal are similarly constructed. They cacli have two parallel chambers separated by a wall 6ome 60 feet thick, one chamber to be used by vessels going up, and tlw other by vessels going down. The total length of each chamber will allow a vessel 1000 ft. long to pass through, but each chamber can Le subdivided kuto two comportments of about 600 and 400 feet respectively, thus obviating the necessity ol emptying or" filling—as the caso may be—tlie entire chamber merely to allow a vessel perhaps only 300 ''eet long to, pass through, thereby economising water as well as lessening tlie time in transit. Tho width of tho chambers is 110 feet, and the lowest depth where fresh water is used is 41it Bin., and salt water 40ft. Tho water is brought in and out of the chambers by means of largo tunnels (18 feet in diameter), lengthwise through tho centre of tho side and centre walls, and is carried from them through others which branch out laterally and communicate with the chamber through openings in the floor, the, flow being controlled by gato-valves above. To raiso the water, the valves at the lower or "down-stream" end are closed, and those at Ihe other end opened, thus enabling the-waters from the. higher levels to fill the lock; whilst to lower it, the lower end valves are opened and the "upstream" end closed, and the water inside being then higher than outsido empties into the tunnels referred to until at the lower level of the outside waters.. It is estimated that the inflow will raise the water in the locks at tho rate of two feet a minute. With a view of saving water the tunnels in the centre walls have been so devised that by the operation of the valves where one chamber has to be filled while its parallel has to be emptied the water of tho latter can pass into the former. Protecting the Locks. For protective purposes guard-gates have ten erected at both ends of each of ■the locks, and with a view of safety as well as the facilitating of navigation, the jentre-walls have been extended for a considerable distance beyond the lockchambers at each end. To these centre walls vessels will tie up, and from that point until through the locks cease to use their own propelling power. Electric motors are to supply, the power, and these will run both on the side and centre walls. When the locks are. ready for tho vessel tlie centre motors will bring her up to the spot at which-the side motors can hook on to her and thereafter four motors—two at each side, one ahead, the other astern—will tow and guide her into lier place within the chambers. The object of these precautions is tho safety of the locks, and particularly of the gates. Further precautions have, however, been taken; should a vessel on approach over-, run herself, before striking the lock gates she will collide at right angles with a chain—the links of which are forged from three-inch iron—extending across tho entrance, and which is aftached i to large hydraulic cylinders, situate within the buildings of the lock walls, tho resistance of these cylinders is estimated to be sufficient to pull up a vessel of 10,000 tons, going at four miles an hour, in 70ft. When all is in- readiness for a vessel's ingress or egress the chain is lowered and automatically falls into a groove on the floor. Should a vessel escape the chain and ram the gates, it 'is, to begin with, only the outer or "guard" gates,-that she .will injure, unless she has considerable "way on," in which case she might, oi course, ram and destroy tho inner gates, and so cause great destruction, as, should from this or any other cause a free waterway between the two different levels at each end of the established, the position would bo little short of disastrous. It is computed that the water would pass through the locks at the rate of 90,000 cubic feet per second. In event of 'such a catastrophe happening, a dev.ee known as an emergency dam has been provided, which can bo swung across the entrance to tlie locks as though it were a swing bridge. From the lower part of this a skeleton gate or barrier would be lowered to the bottom, and when in position slides would be dropped into it. It is estimated that the effect of this, would be to sufficiently check the rush of water to allow of a caisson (kept in readiness) being towed to the spot and sunk, thereby absolutely closing the entrance and precluding any water passing through.

The Gates of the Locks. The gates of the lock's are in themselves vast constructions, each consisting of a pair of half-gates. They aTc all cellular in construction, the lower part being an air-tight chamber, and thereby reducing the weight when the water is low; the upp«r half is so constructed as to allow tho water as it rises inside the chamber to. flow, into the gates,' so increasing their weight as the weight of water within the chamber, is increased. There are 92 haltgates each 7 feet in thickness and 6o feet wide.' They range in height from H to 82 feet, and if they were all stacked flat on the 'top of one another would, make a column m feet high, and would weigh about 58,000 tons. The height of this column would ho only 5 feet less than that of Mount Victoria. , Tho locks are well advanced towards completion. The concrete' work, of which the main structure consists, is practically finished; the cog-rails for the electric motors are made, and the bulk of the machinery for the locking operations in the interior of the wallsappears to be in place. The erection of the gates is progressing rapidly, so much so that the writer was able to cross the chambers of the Pucdro Miguel lock with the aid of a plank or two laid on tho gates, and look down on theslimy bottom, which the scales, painted in white on the side of the wall, showed was 76 feet beneath him. It was uncanny work walking about these lock walls, in the surface of which were innumerable openings into the interior, with great heaps of timber and machinery to be dodged, whilst scores of labourers hurried backwards and forwards in every direction. The officials were courteous to a degree, and.were ready to show visitors all any anything. A voyage into the interior offered a -tempting study of the. internal workings-of this vast machine, but time was short, and a climb down and then up an iron ladder sunk into a wall 7G feet high, cooled one's ardour. The rays of a tropical sun poured straight down, unchecked by any sign of cloud, and the thermometer registered 6omowhera about 130 degrees. Whilst the suggestion to go below certainly sounded tempting, the Erospect of coming up again seemed a disint one, and as an alligator over 12 feet in length had been, found wallowing in the slime of this very lock only an hour earlier, and 'was seen shortly afterwards in process of being skinned, the proposition was too unattractive to bo taken on.

Divisions of the Canal System. For the purposes of description it will be as well to divide the whole of the canal system into five .sections, although, so far as the waterway itself is concerned, there are actually only four divisions, but if treated as consisting only of four, it will bo necessary to merge into one, two of the greatest operations in progress. Beginning at the Atlantic side, the first section comprises a sea level length of about seven miles, from' the ocean to the first locks at a place called Gatun. The second section is at the high level—the canal surface being 85ft. above sea level—from Gatun to Bas Obispo, a distance of about 23 miles; and is known as tho Gatun Lake. The third section consists of what is known as the Culobra Cut, and txtonds from Bas Obispo to the lock atPuodro Mignel, a distance of about nine and a half miles. This, section will also be at the high level, there being no lock between Gatun and Puedro Miguel. The fourth section is about ono mile and a half long, extending from . Puedro Miguel to the lock at Mira Floras, and will be known as the Mira Flores Lake. The fifth and last section is on the lovel of the Pacific Ocean, extending from Mira Flores out to deep water, a distance of about eight miles. The work of the 'first section has consisted chiefly, with the exception of that portion nearest to Gatun, in deepening a channel through Limon Bay, making a watcrwav 41ft. deep and 500 ft. wide, which, looked at from Gatun, presents the appearance of a river running up inland through a dense mass of mangroves.

Gntwn Wake. The second section Is that part of tho JuglwYator level of tue canal extending

for about 23 miles from Gatun lock to Bas Obispo, on the western side, and Ganiboa on tho eastern. Practically the whole area is a natural basin, at the southern end of which, on the eastern side, is tho Chagres Hiver. This Lasiu consists of low hilly country, or, rather, a conglomeration of small Kills, through which the Chagres flowed to the sea, and it is this basin that the I.C.C. has turned into a huge lake, by damming back from the sea the waters of the Chagres.. This will ijivo a depth of water varying from 45 to about 90 feet, the width of tho channel through tho lake for the first sixteen miles is 1000 ft, but it tapers off gradually until for the last mile it is not moro than 500 ft. The surface of tho water will be 85ft. above sea level, and at this elevation the total superficial area of the confined water or lake (known and spoken of as Gatun Lake) will be about 164 square miles; included in this will be the area of water comprised in Section No. 4. In estimating the time of transit at twolvo hours through tho canal, it has been assumed that vessels will proceed at full speed through tho lake. The flooding of. this large area to such a great depth has necessitated "tlio relocation of the Panama railroad at a higher elevation, and as the old road crossed the site of the Gatun Locks, its 'wholo course has been altered, and it is now on the eastern, bank of the canal instead of the western, as in the past, up to Obispo; for a great part of the distance tho road is laid ■ through the Gatun Lake.

Gatun Dam and Locks. The greatest work in connection with the formation of this lake Has probably been the construction of the Gatun dam, erected for the purpose of confining the waters of the Chagres. This structure crosses what may be called the mouth of tho natural basin of this area, and is of such magnitude as to render the conception of it by the use of the word "dam" impossible. It is moro like the base of a, small mountain. The distance between, the two nearest hills at the opposite sides of the mouth, of this basin was 2500 yards in length, nearly one milo and a half, and a bank this length, has had to be erected to withstand the pressure of .tlie 160 square miles of water. To ensure sufficient stability, tho thickness of the bank at its base is'2loo feet, whilst at water-level on the lake side it is 100 feet thick. The total height is 105 feet, the top being about 20 feet above the normal level of tho water in the lake. This dam is constructed of two outer walls,. the. material for which was taken from the cuttings in the higher, levels.. Theso walls were so constructed as to leave at the base a gap of about 1200 feet, and this gap has been, and is being filled, by the spoil taken from the ted of tho channel of tho canal through the lake by means of suction pumps which lift tho spoil, of which about 80 por cent, is water, and foroo it through pipes into the gap in the dam, the solid matter here sinks, and thowater is drained off. This internnl.fifling, or iuner core, is looked upon as the watertight wall of the dam. ' • It has been already mentioned that there aro threo locks connecting tire "high level" and the Atlantic. These aro all in this section at Gatun, and aro really one structure, forming what is termed a."flight" of three locks. Thus vessels approaching from the high, level end will be "locked" in the first or high level chamber, where they will be ed about one-third of th« distanco of SS feet, bringing them to tho level of the water.,in. the middle or second-chamber, into which they will pass and there be lowered to the level of the water in the third chamber, in which they will -<bo lowered to the level of the Atlantic. • The necessity for having a "flight of threo," instead of a single lock, is probably Tie-, cause the pressure of so great a volume of water would involve too great a strain on the gates.