132 LECTURES TO SCIENCE TEACHERS. 



atom of carbon, and goes out as carbonic oxide. There are 

 these great difficulties in actual manual firing, and it is to 

 get over them that the engine-driver at the Koyal Agri- 

 cultural trials fires once in every two minutes, and obtains 

 practical uniformity from the beginning to the end of the 

 live hours' trial. But, as I say, this is impossible in practice. 

 When fuel is dealt with in other ways it is far more 

 manageable. It is all surface, if I may say so, when it is 

 reduced to impalpable powder, because the surface of a given 

 weight in that form may be popularly said to be infinite as 

 compared with the surface of lumps of coal, and therefore 

 when working on this system you can properly proportion the 

 supply of powder and of air to each other, and so obtain ex- 

 tremely good results by this mode of firing. At present I 

 am sorry to say that Mr. Crampton is not helping us in the 

 economic generation of steam, for he is devoting himself to 

 the application of his system not to the obtaining heat for 

 steam-engines but to the production of the high temperatures 

 required in the puddling of iron. In the case of the liquid 

 hydrocarbons, and in that where the fuel is converted into 

 gas, as in Dr. Siemens' producers, it is also possible in prac- 

 tice to regulate with nicety the amount of the air, and it is 

 from this power of regulation that the large percentage of use- 

 ful effect has been got from liquid fuel, and that the high 

 results arising from the combustion of gas have been got even 

 when that combustion is unaccompanied by the regenerative 

 system of Dr. Siemens, which system has caused the vast 

 economy of fuel which has been obtained since its introduc- 

 tion in many of our most important metallurgical and other 

 processes. 



