The boiler, frame-plates, and some of the brass fittings, were purchased, but the whole of the machine work and fitting was executed on the spot. The cost of all material, the hours of labour and engine power, interest on tools, &c., were all carefully booked, and it will probably not be far from a fair trade price for the engine if 10 per cent, for drawings and patterns, and 20 per cent, for profit, are added to the cost given above, thus bringing the amount to about £400.
The working of the radiating gear of engine No. 2 proving so satisfactory, I elaborated the principle so as to apply it to an eight-wheeled locomotive. (No. 3 in the table.) In this case both of the middle pairs of wheels have the traversing motion already described, but, instead of the leading and trailing wheels being radiated from one central pair, the second pair of wheels radiates the leading pair, and the third pair of wheels the trailing pair, thus forming a mechanism practically equal to a double bogie. By this arrangement an eight-coupled engine is obtained capable of passing round curves as severe as may be necessary. In the present instance, the travel is constructed for a minimum radius of 25 ft. The details of the engine are similar to those of No. 2, but numerous improvements have been effected, into all of which it would be tedious to enter. It may, however, be mentioned that the ends of all the crank pins are boxed in by the connecting and coupling rod brasses, to exclude dirt. A steam water-lifter has also been added, by which the tanks can be filled without delay during frost.
The blast-nozzle is made adjustable by raising or lowering an internal cone. Owing to the steep gradient before alluded to, it was impossible to get a fixed size of nozzle that would keep up steam with a light load on the level, without being so contracted as to lift the fire off the bars on the incline.
The boiler fittings have been made as symmetrical as possible, and circular nuts have been substituted for hexagon, as more easy to clean. The water-gauge glasses are put in through the top cock and fastened by a single cap nut, thus doing away with the usual external glands. The steam brake has a 5 in. cylinder, and the rigging is arranged to swing with the traversing wheels.