The following text may have been generated by Optical Character Recognition, with varying degrees of accuracy. Reader beware!

CAISSON FOR REPAIRING PROPELLERS. With the advent of the fast twin-screw steamship Cayuga in the ttans-lake On- tario trade, the Niagara Navigation G6! found itself face to face with the possi- THE Marine. REVIEW in case of such a contingency, the com- pany has had designed and constructed what may be described as two portable ay -doéks 'for' the 'exclusive' use of ae Cayuga." OE Re i artafigethien' 4g © alt! i gétlious one, and cdnsists/4f! two eanllbue bility of having the vessel laid off for an indefinite period in case of the breaking of one or more blades of her propellers, owing to the fact that the nearest dry dock is at Kingston, Ont., and that the dock might not be available when re- quired. With a view, therefore, of pro- viding for the speedy repair of the vessel each about 16 by 12 ft, and -having depth of about 12 ft., one side being en- tirely open. The upper of the accom- panying illustrations shows the two cais- sons prior to launching, that in the fore- ground being for the port side, and that in the rear being for the starboard side. The end of the caisson shown to the right " in fhe 'iNustration is imiched with. a straight edge, which will fit close up to the' GHSPP OH the edge of the floor ak: the caiss SOF di is also , _ straight so as to fit be; neath, 'the keel, the. edge of the forward end being shaped to correspond _ to the curvature of the hull. The two. gates or doors showing in the lower illustration, are cut in the, forward end to, admit . of the. propeller shaft . being brought. inside the caisson, an aperture being arranged. 0 - at, 'to. fit around the shaft. , The, upper door opens | 'upwards and. the ower. cone downwards. These are opened to admit the shaft, and are then 'eloge ys chain attachments. Each caisson is coining of steel framework, planked on' the outside and braced internally by heavy timbers. When it is required: to replacera blade of the propeller, whichever caisson it is neces- sary to use will be towed to the side of the vessel and, by means of chains: passed under the hull,: will be drawn into: posi- tion, rods and turnbuckles attached to the . upper portion of. the. vessel' being used to hold it in position, The edges" of each caisson, and of. the. hole through: which the shaft passes, are fitted with' heavy rubber bands for the purpose 'of aiding in 'making' a watertight junction, The top of the caisson, when 'fixed in position for operation, ae about 18. inches above the water level. After. the caisson. ds "affixed, and the doors: closed, the water is pumped out and the 'workmen are enabled ' to get inside and to 'proceed with their work. To facilitate' their operations two: plat- forms are provided in each caisson, so that. it is not necessary. to pump them entirely clear of water. Each caisson weighs about three tons, and has a ca- pacity of about 12,000 gals. of water. It can therefore be gathered that as this quantity of water is 'pumped out, the pres- sure on the outside will increase, and aid in holding the caisson in place, and in ensuring the junction with the hull being watertight. The lower illustration shows a portion of the interior of the port cais- son, viewed from the stern end, and with the gates closed, the hole for the shaft being in the center of the forward end. The caissons were designed and con- structed under the supervision of B. W. Folger, manager of the Niagara Navi- gation Co., by Jno. Whalen. os The device is also valuable for. giving, access to. the stern shaft. bearings, The, idea is an ingenious | one, and the. tests made show that it is thoroughly prac- ticable. -- could. be utilized for adjusting aew 'blades to single screw steamships, and it might. be possible to so develop 'the idea, by means of screws and 'double planking to. construct a caisson in such a way that it. could be utilized for a number of 'vess Is, A single caisson, constructed SO. as to fit around the stern of a "vessel