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 is utilized in propelling the vessel. In spite of all these improvements I have mentioned, there remains the serious question of defects in the material, due to variety of quality and the extreme care that has to be exercised in all the stages during construction of crank or other shafts built of iron. Many shafts have given out at sea and been condemned, through no other cause than _original defects_ in their construction and material. The process of welding and forging a crank shaft of large diameter now is to make it up of so many small _pieces_, the _best shafts_ being made of what is termed scrap, representing thousands of small pieces of selected iron, such as cuttings of old iron boiler plates, cuttings off forgings, old bolts, horseshoes, angle iron, etc., all welded together, forged into billets, reheated, and rolled into bars. It is then cut into lengths, piled, and formed into slabs of suitable size for welding up into the shafts. No doubt this method is preferable to the old method of "fagoting," so called, as the iron bars were placed side by side, resembling a bundle of fagots of about 18 or 20 inches square.