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8 MARINE REVIEW. No Delay on Account of the Canal Accident. Editor MarInk REVIEW: Iam in receipt of yours of the 20th inst., asking information as to the cause, nature and extent of the accident which happened on the 13th inst., to the miter-wa'l of the upper guard gates of the 800-foot lock, St. Mary's Falls canal. ; The upper guard gates and miter-sill had reached that stage when it was desirable to test them, both in regard to construction and adjust- ment. Accordingly the gates were closed on the miter-sill,and water was pumped into the fore-bay above them. When the head of water reached a stage of 14% feet above the miter-sill, the top course of masonry in the miter-wall was subjected to a head of 18% feet at the level of its bed, and the upward pressure (about 1,150 pounds per square foot) proved sufficient to lift that course, which it did with a violent rupture of the mortar be- tween it and the next lower course. The rupture extended throughout the bed, to within about two stones of either end, where the vertical joints yielded. No other vertical joints were disturbed. The upward pressure of the water on the bottom of the gate had not reached the weight of the gate, and of the water which had been pumped into it, so that the accident was in no degree due to the friction between it and the miter-sill, and the latter was not disturbed in its fitting to the top of the miter wall. The cause of the accident is easily determined. The part of the miter-wall that was lifted, (only a part of the top course,) was laid late last fall, and before the mortar had thoroughly dried out freezing weather came on. The low temperature of the winter caused the stone to con- tract and disrupt, but probably not to great extent, the bed which after- wards gave way. The crack was so minute as to escape attention, but stilllarge enough to admit water under the pressure due toa head of 18% feet. Although a mere film it was, nevertheless, sufficient to transmit the pressure to the full extent of the disturbed bed, and the stones forming the greater portion of the top course were lifted as described, thus vio- _ lently extending the crack to the portions of the mortar which had not been involved in the original crack. 'After the accident occurred the water was drawn off, whereupon the course which had been lifted was relieved of the upward pressure and it returned to its original position, sothat an ordinary observer would hardly be able to find the ruptured bed unless he knew just where to look for it. Ifthe top course had been bolted to the others the accident would not have occurred ; nor would it have occurred if the mortar bed bonding it to the course below had been intact. The strength of the mortar was ample, as is shown by the fact that the vertical joints were not ruptured except at the two ends of the uplift. The remedy is a simple one, and easily applied. It is to drill down through the wall for a depth of 13 feet aud insert 100 1%/-inch bolts thus tying together the whole 14 feet of the height of the wall. The combined strength of the bolts will be such that the entire wall might be lifted by them. It will not be necessary to reset a single stone, nor will the cost of the bolting be any greater than if the bolts had been placed in the first instance. From the foregoing it will appear that the accident was neither ex- tensive nor serious, and that the cost of the bolting will be no greater than if it had been done in the first place. It will not result in a single hour's delay in the completion of the lock. The sensational statements which have appeared in print in regard to the matter have no just foun- dation whatever. It should be remembered that the very object of the test was to ascertain if there were any weak points, and, if so, to apply the requisite remedy. As far as I am concerned I am glad that the defect developed now rather than at some future time when serious delay might have occurred. I may add that every set of gates will be tested in the same manner, and it is not impossible that we may find weak spots in other places, although I do not think we will. Detroit, Mich., Sept. 21, 1895. O. M. Pox. Compressed Air for Fog Signals. For some time past the light-house board has been experimenting at the Staten island station with a fog horn apparatus, in which compressed airis used instead of steam, and which is intended for application to light-ships as well as shore stations. A gas motor of the Horns-Akroyd type is used for compressing the air in a tank, frem which it is liberated through the horn. To assure themselves of the efficiency of the motor on shipboard the officials of the light-house service have decided to have one of the motors and its appliances placed on the Winter Quarter shoal light-ship off Atlantic City. Two engines have been put on the ship, One is a duplicate of the other, to replace the one in operation in case of accident. It is believed that the engine will be as successful.on a rolling as on a stationary base. The engine is moved bya succession of gas explosions in the piston. By the use ofa Clayton air compressor, air will be forced into the large tank to be drawn upon as occasion re- quires. The blast with the new generator and apparatus will last five seconds, and will be repeated each minute during a fog. The / greatest advantage, perhaps, which the new generating power pos- sesses is the quickness with which the sound can be made. Under the old method it took from forty-five to sixty minutes to light the fires under the boilers for the generation of the steam to blow the horns. Now in five minutes air can be compressed in the tank, anda blast of the maximum force can be given immediately. The tank is left full of compressed air after itis used, and contains enough power to keep the horn going for ten minutes. Thns it will be seen that under the new method the blowing of the horns is practically continuous. They can be started before the fog rolls down upon the keeper and kept blowing steadily until the fog lifts. The power can readily be shut off during any temporary lifting of the fog, while formerly it was necessary to keep the fires up and banked for along time, so as tobe sure of being in readiness should the fog roll down again. If experi- ments on the light-ship at Winter Quarter shoal prove successful the new apparatus will be quite generally adopted. Compass Bearings on Lake Ontario. One of the latest circulars from the United States hydrographic office says: 'Tt is very plain that compass bearings cannot be closely relied upon at the eastern end of Lake Ontario. In the neighborhood of the Main Duck islands it has been frequently observed that there is a great deviation of the compass, sometimes as great asa point ata time. This renders navigation very uncertain in thick or foggy weather. This devi- ation is due, most probably, to numerous superficial deposits of iron ore. An examination of the magnetic observations that have been made in the Province of Ontario, Canada, shows that there are numerous localities in the region immediately above Lake Ontario where there are considerable local irregularities. The dips at Kingston and Belleville, at the foot of Lake Ontario, and at Prescott,on the St. Lawrence river, are among the most irregular recorded on the magnetic survey of Canada, and it is cer- tain that both the compass and the dipping needle will be subject to notable and irregular local influences in the eastern portion of the lake. At Brockville, about twelve miles west of Prescott, and at Cornwall, about forty-six miles east of that place, the anomally disappears." Stocks of Grain at Lake Ports. The following table, prepared from reports of the Chicago board of trade, shows the stocks of wheat and corn in store at the principal points - of accumulation on the lakes on Sept. 21, 1895: Wheat, bushels. Corn, bushels. OHICA RON ere eee 14515 .000 1,481,000 MUUCH ene vcntresescecsuccscecscccecsinceie: AZO 00m eo ie ce ee IVE WW AWK Cticc ccs ces hace testa cc sceets fon ccces ANA OO Oi re Se Oe Se oae WDEULOlU restos ace cac sccssts sees: ddccess ose 462,000 24,000 POCA Or etaetc Geese csc aeconc cies csc enttees 948,000 138,000 Bika ONsetanectetsccescee ccc sess consectencies: 2,079,000 294,000 otal aci:s bast Bb chee h Fix sap bit 23,144,000 1,937,000 As compared with a week ago, the above figures show at the several points named an increase of 540,000 bushels of wheat and 207,000 bushels of corn. Big Steamships of the World. The following data regarding the world's greatest merchant vessels and vessels of war may prove valuable for reference: MERCHANT STEAMSHIPS, Name. Length Beam Displacement. G@reatwasternct. saceeccetdecuccstes 680 feet 88 feet 24,000 tons Step WOMis tread hia adh ace wa coae cava 535 feet 63 feet 16,000 tons Wann ati gist so. cig syebiecsec- «ht aas 600 feet 65 feet 18,000 tons Teutonic. Risnaeale sais etisistews teases of 065 feet 57 feet 12,000 tons PATS deter ance x asdeutel socasehoulie 528 feet 64 feet 13,000 tons : WAR VESSELS. Cohtumrb ia. ee Ak, Oke 412 feet 58 feet 7,475 tons SArdennal skis eet ee as, 400 feet 77 feet 13,251 tons Royal Sovereiga.is....0..f.000 380 feet 75 feet 14,150 tons Mernible AM CH Oe ALAS: 500 feet 72 feet 14,200 tons ING Wy ORA Mire ieee dak Bit 381 feet 65 feet 8,480 tons Germany's mercantile marine is now far greater than that of France, and is second only tothe British. In 1894 it measured 1,485,000 tons against 9,585,000 tons for England. The steamer tonnage, which in 1888, was less than the French, amounted to 860,000 tons against 466,000 tons for France. During the months of July and August the average working force at Cramp's ship yard, Philadelphia, was 6,000. LAKE ERIE AND LAKE- ONTARIO ON ONE SHEET, THE THIRD OF THE HYDROGRAPHIC OFFICE SERIES OF CHARTS, IS NOW IN PRINT AND MAY BE Hen FROM THE MARINE REVIEW, 516 PERRY-PAYNE BUILDING. PRICE CENTS. : a RR at