WILLIAM SIEMENS, F.R.S. 205 



ostliat of the first proposer, the combustion was produced gradually ; 

 the gases were ignited as they flowed into the heating cylinder. In 

 the third type, the gases, after being compressed and mixed, 

 admitted into the working cylinder, and suddenly exploded. 

 With reference to the early engine which Dr. Siemens constructed 

 in 1860, Plate 87, the author had stated that it combined other 

 rl. 'incuts, which were entirely wanting in the gas-engines of the 

 present day. The gas-engine of the present day, taking either of 

 the three types, was, in his opinion, in the condition of the 

 steam-engine at the time of Newcomen. The fuel was burnt in 

 a cylinder which it was attempted to keep cold by passing water 

 over it, and it was easy to conceive that the heat so generated, 

 was only partly utilised for maintaining the state of expansion of the 

 heated gases, the cold sides of the cylinder taking a good half of 

 it away at once, thus causing a great loss. Then there was another 

 palj >uble loss in these engines. After expansion had taken place, 

 after half the heat had been wasted in heating a cylinder which 

 was intended to be kept cool in order to allow the piston to move, 

 the gases were discharged at a temperature of 1,000, or in the 

 best types about 700. That amount of heat, representing in one 

 case one-half and in the other two-thirds of the total heat gene- 

 rated, was thrown away. This was heat which could be saved and 

 made useful. Instead of commencing the combustion at a tem- 

 perature of 60, if the heat of the outgoing gases were transferred 

 to the incoming gases, combustion might commence at a tempera- 

 ture of nearly 1,000, and the result would be a very great 

 economy. In the engine which he constructed in 1860 all 

 those points were fully taken into account. The combustion of 

 the gases took place in a cylinder without working a piston, and in 

 a cylinder that could be maintained hot, and the gases, after having 

 complete expansive action, communicated their heat by means of 

 a regenerator to the incoming gases before explosion took place. 

 Although the engine was not worked with ordinary gas used for 

 illumination, but by a cheaper kind made in a gas-producer, he 

 then thought that a gas-engine constructed on that principle 

 would prove to be the nearest approach to the theoretical limits 

 which could never be exceeded, but which might exceed the limits 

 of the steam-engine four or five fold. The engine promised to give 

 very good results, but about the same time he began to give his 



