Nikola Tesla U.S. Patent 517,900 - Steam Engine Patent Wrapper Page 12

84 cylinder at defined intervals and thus any tendency to a change of the period of vibration in the main engine is overcome. The control of the main engine by the engine of constant period may be effected in other ways of which Fig. 2 will serve as an illustration. In this case the piston of the controlling engine constitutes the slide valve of the main engine, so that the latter may be considered as operated by the exhaust of the former. In the figure I have shown two cylinders A A' placed end to end with a piston B and B' in each. The cylinder of the controlling engine is formed by or in the casing intermediate to the two main cylinders but in all other essential respects the construction and mode of operation of the controlling engine remains as described in connection with Fig. 1. The exhaust ports à d however, constitute the inlet ports of the cylinders A A' and the exhaust of the latter is effected through the ports m, in which are controlled by the pistons B and B' respectively. The inlet port for the admission of the steam to the controlling engine is similar to that in Fig. 1 and is indicated by the dotted circle at the centre of the piston b. An engine of the kind described possesses many and important advantages. A much more perfect regulation and -7