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16 properly come within the scope of the title of this paper. For some years past cold flanging has been largely adopted in lieu of angle at- tachments in double bottoms of steam- ers. Floor-plates have* been flanged at their upper and lower edges, and inter- costal plates have been sometimes flanged against the floors and sometimes flanged on their upper and lower egdes. It is generally admitted that recourse to flang- ing involves the necessity for the best workmanship and the most closely-fitting surfaces. It is also generally recognized that flanging does not provide the same rigidity of connection as an angle-bar. But it is believed by many that the asso- ciation of flanged materials, as in the structure of a cellular double bottom, does produce under proper conditions an efficient combination, and one that is suit- able for resisting the stresses coming upon it, either afloat or on well-laid blocks in a dry dock. It is, however, not so generally conceded that flanged floors are so well able to resist the stresses re- sulting from grounding or stranding as floors riveted to frames and_ reverse frames. This is an important question, and attention to it is now invited. Vessels fitted with cellular double bot- toms usually have after-peak ballast- tanks for trimming purposes, and some have fore-peak ballast-tanks also. In each case, valuable use is thereby made of a space which can be employed for but a few other purposes. Certain pre- cautions are, however, found necessary in view of the fact that these peaks are sometimes only partly filled with water. It need hardly be remarked that when at sea they should always be either quite full or: quite empty. If quite full, the stresses due to the water-pressure with- in the tank are about balanced by those due to the water-pressure on the outside. If quite empty, the stresses upon the shell-plating and framing are no greater than those ordinarily experienced else- where on the immersed portion of the hull. But when the peaks are only par- tially full of water, the violent move- ments of the vessel in a seaway set up stresses of a destructive character. To minimize the results of these, deep wash- plates should be fitted, and these should be efficiently secured. It is further de- sirable that the rivets through the frames and shell-plating should be more closely spaced than elsewhere in the sides and bottom of the vessel. Even with such precautions, damaging stresses result from peak ballast-tanks being only part- ly full of water when at sea.: It has of late years been usual to fit midship deep tanks in cargo-steamers, in order to obtain the necessary immersion when the vessels are in ballast trim. Such deep ballast-tanks sometimes con- tain upwards of 1,000 tons of water. If 'as possible. THE Marine RevIEW they are kept full of water, the stresses upon the materials of which the tanks are built are such as may easily be pro- vider for; but if only partly full when at sea, then, having regard to the much greater breadth of the vessel where the tanks are situated than at her extremi- ties, the violent motion of the free water is even more damaging than in the peaks. In order to reduce the longitudinal movement it has been usual to keep the length of an individual tank within mod- erate limits, and in cases where, say, 2,000 tons of water have to be carried in that way, to build two tanks rather than only. one. Also, to moderate the effect of transverse movement, it has been usual to fit a longitudinal middle- line bulkhead in the tank, extending from the top to the bottom. It has also been usual to additionally strengthen the sides of the vessel by web frames in way of deep tanks. The rivets through frames and shell have been more closely spaced than elsewhere in the vessel, except the peaks; and, of course, the transverse bulkheads bounding the deep tanks have been very thoroughly stiffened. Cargo is carried in these deep tanks when they are not used for water-bal- lasting purposes; and consequently there has always been a natural desire to break the stowage as little as possible inside the tank, and to make the work of get- ting the cargo in and out of it as simple In order to effect this, the middle-line longitudinal bulkhead has in some cases been omitted, and there is a growing desire to dispense with it al- together. Were all men _ trustworthy, so that it might be definitely ensured that a deep tank would always be completely filed with water when at sea, the omis- sion of the longitudinal partition bulk- head would not be a matter of much mo- ment, and the loss of stiffening to the transverse bulkheads resulting from the omission could be easily supplied in some other way. But in view of what ex- perience shows to be a not unusual treat- ment of ballast-tanks at sea, it is .sub- mitted that the fitting of the middle- line longitudinal bulkhead is so desirable as to override any objection to it aris- ing from inconvenience or broken stow- age. : When deep tanks are not fitted in a steamer, and when the weight of the water carried in the after-peak tank is not sufficient, acting in conjunction with the other water ballasting, to give the necessary immersion to the screw pro- peller, it has been usual to _ supple- ment water with shingle or grav- el, ballast carried on deck. and thrown overboard on entering the load- ing port. To save the expense of taking this shingle ballast, or of building a deep tank in the steamer, some Owners have authorized the masters of their ves- sels to admit water into the after-hold, by taking off some manhole covers from the inner bottom, and then opening the sea-cock until a sufficient quantity of water is admitted for obtaining the de- sired immersion of the screw-propeller. It has not been usual for the water ad- mitted to extend above the top of. the shaft tunnel, which latter thereby serves a useful purpose in partially checking the movement of the water due to the rolling of the vessel. Even with that limitation, the movement of such a body of free water has caused damage by washing up ceiling and sparring, and reducing them to pulp; and it cannot be doubted that the structure of the vessel might al- so be damaged under such conditions. It may be conceded that at a time of peril, with a vessel near a lee-shore and the propeller insufficiently immersed to get ber into a position of safety, it might be allowable to choose the less of two evils, and admit free water into an after- hold in order to obtain the desired deep- er immersion But a course which might be resorted to in order to save life and property should not be adopted as a normal condition of navigation in ballast, when attended with such evil consequences as are found to occur in this instance. Of late some very valuable arrange- ments, both from a structural as well as from a navigator's or a shipowner's point of view, have been introduced into cargo- steamers. One of these is the Dixon and Harroway system of wing tanks for carrying water-ballast, and another is known as McGlashan's side-tank system. The figures on the walls show ..the two arrangements, which it is thought are well worthy of consideration. A primary object in both systems is to carry water- ballast at a higher level in the vessel than is possible in the ordinary double bottom, and so reduce the stability, which is often excessive in the modern-broad and shallow steamer when in ballast trim. Other important objects.are alsé served. In both cases the tonnage meaurement is reduced by the arrangement from what it otherwise would be; and as such ves- sels are intended for carrying dead- weight cargoes, the available hold-space is amply sufficient for their owner's pur- poses. Dixon and Harroway's arrange- ment serves also the purpose of self- trimming, and both it and McGlashan's system add materially to the structural strength of the vessel. As regards the Dixon and Harroway arrangement, it will be evident that with a reasonable spacing of transverse bulk- heads, giving holds of not immoderate length, the fore-and-aft girders formed by the wing tanks and continuous hatch- coamings enable pillar suports to be dis- » pensed with. This is a valuable feature in a cargo-steamer.