84 SCIENCE IN BHORT CHAPTERS. 



In burning the gas derived from coal we obtain its 

 illuminating power directly, and if we burn it properly 

 we obtain nearly all. The coke residuum is also directly 

 used as a source of heat. The chief waste of the original 

 energy in the gas-works is represented by that portion of 

 the coke that is burned under the retorts, and in obtaining 

 the relatively small amount of steam-power demanded in 

 the works. These are far more than paid for by the value 

 of the liquid hydrocarbons and the ammonia salts, when 

 they are properly utilized. 



In concluding my narrative, I may add that after Mr. 

 Starr's death the patentees offered to engage me on certain 

 terms to carry on his work. I declined this, simply be- 

 cause I had seen enough to convince me of the impossi- 

 bility of any success at all corresponding to their anticipa- 

 tions. During the intervening thirty years I have abstained 

 from further meddling with the electric light, because all 

 that I had seen then, and have heard of since, has con- 

 vinced me that although as a scientific achievement the 

 electric light is a splendid success its practical application 

 to all purposes where cost is a matter of serious considera- 

 tion is hopeless, and must of necessity continue to be so. 



Whoever can afford to pay some shillings per hour for 

 a single splendid light of solar completeness can have it 

 without difficulty, but not so where the cost in pence per 

 hour per burner has to be counted. 



I should add that before the publication of King's 

 specification, Mr. (now Sir William) Grove proposed the 

 use of a helix or coil of platinum, made incandescent by 

 electricity, as a light to be used for certain purposes. 

 This was shown at the Eoyal Society on or about December 

 1, 1845. 



Since the publication of the above in 1879, 1 have learned, 

 from a paper in the " Quarterly Journal of Science," by 

 Professor Ayrton, that in 1841 an English patent was 

 granted to De Moylens for electric lighting by incan- 

 descence. 



