ENGINEERING BEFORE AND AFTER WAR 41 



teeth of machinery for the crushing of stone and other 

 materials, and, in fact, for any purposes where great 

 hardness and strength are essential. 



Investigation of Gaseous Explosions. Brief reference 

 must also be made and it will be gratifying to do so 

 to the important work of one of the Committees of the 

 British Association appointed in 1908, under the chair- 

 manship of the late Sir William Preece, for the investi- 

 gation of gaseous explosions, with special reference to 

 temperature. The investigations of the Committee are 

 contained in seven yearly reports up to 1914. Of the 

 very important work of the Committee I wish to refer to 

 one investigation in particular, which has proved to be a 

 guiding star to the designers and manufacturers of in- 

 ternal combustion engines in this country. The members 

 of the Committee more directly associated with this par- 

 ticular investigation were Sir Dugald Clerk, Professor 

 Callendar, and the late Professor Bertram Hopkinson. 



The investigation showed that the intensity of the heat 

 radiated by the incandescent gases to the walls of the cyl- 

 inder of a gas engine increases with the size of the cyl- 

 inder, the actual rate of this increase being approximately 

 proportional to the square root of the depth of the radiat- 

 ing incandescent gas ; the intensity was also shown to in- 

 crease rapidly with the richness of the gas. It suffices 

 now to say that the heat in a large cylinder with a rich 

 explosive mixture is so intense that the metal eventually 

 cracks. The investigation shows why this occurs, and by 

 doing so has saved enormous sums to the makers of gas 

 and oil engines in this country, and has led them to avoid 

 the large cylinder, so common in Germany before the war, 

 in favor of a multiplicity of smaller cylinders. 



SCIENCE AND THE WAR 



Four years is too short a time for much scientific in- 

 vention to blossom to useful maturity, even under the 



