and boilers (as well as many other engines of all kinds now placed on board a large mail and passenger steamer), instead of getting many a drenching with sea water, and worried by close attention to one or two hot bearings all the watch.  Compare these results with the following:  In the same service in 1864, and with no blame to the engineer in charge, the crank shaft bearings of a screw steamer had to be lined up every five days at intermediate ports, through insufficient bearing surfaces.  Sea water had continually to be used, resulting in frequent renewal of crank shaft.  Steamers can now run 25,000 miles without having to lift a bearing, except for examination at the end of the voyage.  I would note here that the form of the bearings on which the shafts work has also been much improved.  They are made more of a solid character, the metal being more equally disposed round the shaft, and the use of gun metal for the main bearings is now fast disappearing.  In large engines the only metals used are cast iron and white brass, an advantage also in reducing the amount of wear on the recess by corrosion and grinding where sea water was used often to a considerable extent.

[Illustration:  Fig. 1
               Fig. 2]

Figs.  No. 1 and No. 2 show the design of the old and new main bearings, and, I think, require but little explanation.  Most of you present will remember your feelings when, after a hot bearing, the brasses were found to be cracked at top and bottom, and the trouble you had afterward to keep these brasses in position.  When a smoking hot bearing occurred, say in the heating of a crank pin, it had the effect of damaging the material of the shaft more or less, according to its original soundness, generally at the fillets in the angles of the cranks.  For when the outer surface of the iron got hot, cold water, often of a low temperature, was suddenly poured on, and the hot iron, previously expanded, was suddenly contracted, setting up strains which in my opinion made a small tear transversely where the metal was solid; and where what is termed lamination flaws, due to construction, existed, these were extended in their natural direction, and by a repetition of this treatment these flaws became of such a serious character that the shafts had to be condemned, or actually gave way at sea.  The introduction of the triple expansion engine, with the three cranks, gave better balance to the shaft, and the forces acting in the path of the crank pin, being better divided, caused more regular motion on the shaft, and so to the propeller.  This is specially noticeable in screw steamers, and is taken advantage of by placing the cabins further aft, nearer the propeller, the stern having but little vibration; the dull and heavy surging sound, due to unequal motions of the shaft in the two-crank engines, is exchanged for a more regular sound of less extent, and the power formerly wasted in vibrating the stern