This engine has oscillating cylinders placed between the driving-wheels. Fig. 2 represents a section of one of these cylinders, from which it will be seen that each has two pistons and piston-rods, which are connected directly to the crank-pins. His invention is described as follows in his specification: "Midway between each set of wheels, e and f, is located the oscillating steam-cylinder, g, having its journals, g' and g", supported in the stationary arm, h, which is secured in a suitable manner to the frame, c. To each cylinder, g, is secured or cast in one piece therewith a balanced vibratory beam or truss, i, as shown. Within the cylinder, g, are two movable pistons, k and k', Fig. 2, provided with piston-rods, l and l', and cross-heads, m and m', as shown. "n n are slides for the cross-head, m, on the insides of one end of the truss or beam, i, and n' n', are similar slides in the other end of said truss or beam, for the cross-head, m'. To the driving-wheel, e, is attached a crank-pin, passing through the cross-head, m, and to the driver-wheel, f, is attached a similar crank-pin, F, that passes through the cross-head, m'. o is the slide-valve within the steam-chest, G, which slide-valve is operated forward and back by means of the valve-rod, o¹, the outer end of which is hinged to the upper end of the slotted lever, o², Fig. 1, that is hung at o³, on the end of the balanced and vibratory beam of truss, i, as shown. On the crank, F, is secured an eccentric, that works within the slot of the slotted lever, o², during the revolution of the crank, F, and in this manner imparts the requisite motion to the slide valve, o, to admit the steam into the cylinder, g, alternately between the pistons, k and k', and at the ends of said cylinder, g, so as to alternately force the pistons, k and k', from and toward each other, and thus, in combination with the vibratory motion of the truss, i, impart a rotary motion to the driving-wheels, e and f. [Illustration: SHAWS OSCILLATING CYLINDER LOCOMOTIVE.]