position by a short supporting link; but a guide would be better, as the versed sine of this link will distort the motion. The end of the valve rod joins LOCOMOTIVE ECCENTRIC WITH ECCENTRIC STRAP AND ROD. the block which is placed within the link, and derives its motion from it. Eccentrics and Eccentric Rods.-In figs. 102 and 103 we have an example of the eccentric strap and rod of a modern locomotive. The eccentric is put on in two pieces secured together by cutter bolts; and it is secured on the axle by a key and also by two screw bolts penetrating a short distance into the axle. In Sinclair's Rouen Engines with straight axles the four eccentrics were cast in one piece. Sometimes eccentrics are made of wrought iron, and are steeled by case-hardening. Generally the smaller half of the eccentric is now made of malleable iron, though the larger half may be made of cast iron. When thus formed the weakest part is in. thick. If the eccentric be wholly of cast iron it should be 1 in. thick in the weakest part. In addition to a pinching screw it should be secured by a key, let in. into the shaft, and in. into the eccentric. Most eccentrics have square grooves turned on the edges, into which fits a corresponding internal flange on the hoop or brass. The ordinary form of eccentric and hoop is shown in figs. 102, 103. Mineral Locomotives.-A class of locomotives is employed at collieries, and to carry iron ore and other minerals, of a cheaper construction and a smaller size than the common locomotives. At the Great Exhibition in 1862, Messrs. England and Co. exhibited an engine with 11-in. cylinders, six wheels-four of them coupled-of 4 ft. diameter, and with 153 tubes 12 in. diameter in the boiler. Messrs. Manning, Wardle and Co. of Leeds exhibited a colliery locomotive with |