XII. PRESIDENTIAL ADDRESS. 



internal combustion engine approximately half as mucli' 

 heat has to be generated as white hot flame inside the- 

 cylinders themselves, the problem of doing so is seen to- 

 be of no mean order. 



At present the marine engine is invariably of the- 

 Diesel oil engine type, and so far satisfactory operation, 

 has been secured in sizes up to 200 to 300 horse power 

 per cylinder. As the Diesel engine is unique among in- 

 ternal com])ustion engines, and has only recently become- 

 prominently under the notice of the lay public, a brief 

 description of its peculiar features may not be out of 

 place. In other forms of internal combustion en- 

 gines, the fuel which may be combustible gas or oil 

 in a state of vapour or minutely subdivided is 

 drawn into the cylinder together with the air 

 necessary for combustion. This charge of explosive mix- 

 ture is then compressed by the return stroke of the piston: 

 and caused to ignite at the proper instant by electric 

 spark or other suitable means. 



In the Diesel engine, however, ^the fuel charge is not 

 admitted to the cylinder until the end of the compression 

 of the cylinder charge. The compression of any gas is 

 accompanied by rise of temperature, and in the case of 

 the Diesel engine the compression is carried to such a 

 degree that the air in the cylinder is red hot before the- 

 oil fuel is injected into it. In this way ignition and per- 

 fect combuston are secured without any separate ignition 

 device. Incidentally a higher degree of economy in fuel 

 consumption is secured by the high compression pres- 

 sure than is possible in other forms of internal combus- 

 tion engines and, more important still, cheap crude oils 

 and even tar oils can be readily used. The consumption 

 of oil per brake horse power is less than half a pound 

 per hour as compared with, say, three times this weight 

 of coal which the steam engine requires for the same out- 

 put. The gain in saving of cargo space by the adop- 

 tion of the Diesel engine is then obvious and also the 

 desirability of eliminating .the steam boiler and the stok- 

 ers to feed it. 



