I have now to draw your attention to a new motor of my own invention, of the weight of 124 lb., which, at 1,550 revolutions, gives 31 amperes and 61.5 volts at terminals. The mechanical horse power is 1.37, and the coefficient 373. Ohms. Armature resistance 0.4 w. Field-magnet resistance 0.17 w. Insulation resistance 1,500,000 w. This motor was only completed on the morning before reading the paper; it could not, therefore, be tested as to its various capacities. We have next to consider the principle of applying the motive power to the propulsion of a launch. The propellers hitherto practically applied in steam navigation are the paddle-wheel and the screw. The experience of modern steam navigation points to the exclusive use and advantage of the screw propeller where great speed of shaft is obtainable, and the electric engine is pre-eminently a high-speed engine, consequently the screw appears to be most suitable to the requirements of electric boats. By simply fixing the propeller to the prolonged motor shaft, we complete the whole system, which, when correctly made, will do its duty in perfect order, with an efficiency approaching theory to a high degree. [Illustration: FIG. 1.--RECKENZAUN'S ELECTRICAL HORSE POWER DIAGRAM. Draw a square, A B C D--divide B C into 746 parts, and C D into 1,000 parts, or, generally, let a division on C D be 0.746 of a division on B C, so that we can use the horizontal lines cutting A B as a horse power scale. A B, in the above diagram, gives 1,000 horse power, if the line B C represents 746 volts, and C D 1,000 amperes. Let x = any number of volts, y the amperes, and h the horse power, then h/x = y/100 :. h = xy/746 A fine wire or thread stretched from o as a center to the required division on C D will facilitate references.] Whatever force may be imparted to the water by a propeller, such force can be resolved into two elements, one of which is parallel, and the other in a plane at right angles to the keel. The parallel force alone has the propelling effect; the screw, therefore, should always be so constructed that its surfaces shall be chiefly employed in driving the water in a direction parallel to the keel from stem to stern. [Illustration: Fig. 2--KAPP'S DIAGRAM.] It is evident that a finely pitched screw, running at a high velocity, will supply these conditions best. With that beautiful screw lying on this table, and made by Messrs. Yarrow, 95 per cent. of efficiency has been obtained when running at a speed of over 800 revolutions per minute--that is to say, only 5 per cent was lost in slip. Reviewing the various points of advantage, it appears that electricity will, in time to come, be largely used for propelling launches, and, perhaps, something more than launches.