PLYMOUTH INSTITUTION. 33 



observations on the process of generating heat. As is the practice 

 in most of the coal gas works in the kingdom, the tar made on the 

 station, for which a ready sale could not be found, was consumed, 

 in conjunction with coal or coke, as fuel. Experience taught him 

 that, whilst on the one hand it was a measure of economy thus to 

 get rid of an article, the accumulation of which might prove both 

 offensive and dangerous, yet, on the other, its employment as fuel, 

 by the means hitherto adopted, was a most wasteful process ; since 

 two thirds, and in many cases three fourths, of the tar sent into the 

 furnace was evidently not consumed. Reasoning on the results of 

 various experiments, and assured by them that the imperfect com- 

 bustion of so inflammable a body as coal tar was entirely due to an 

 excess of carbon, it occured to him that since water by decomposi- 

 tion yields hydrogen and oxygen, that fluid if .decomposed in 

 contact with the tar would render its combustion complete. The 

 first experiment was successful, by delivering into a furnace, in 

 which was a clear fire, made with coal or coke, coal tar, in a very 

 fine stream, accompanied by an equal quantity of water, it was 

 found that the whole of the tar might be decomposed. At Lyming- 

 ton the patentee has made, during successive weeks, with one 

 twenty two inch, York, D, retort, 3,800 cubic feet of gas from eight 

 bushels of Newcastle coal, (eighty pounds per bushel) in twenty 

 hours, which is at the rate of 13,300 feet per ton, and 17,100 feet 

 per chaldron. A greater quantity of gas obtained from a given 

 quantity of coal as compared with the usual products in gas estab- 

 lishments, is not the only advantage consequent on these workings. 

 The gas made under these circumstances is of superior density. In 

 many instances its specific gravity has averaged .550. At Salisbury 

 nearly similar results have been obtained : with three twelve-inch, 

 D, retorts, 7,800 feet of gas have been made from eighteen bushels 

 of Newcastle coal in twenty-four hours, averaging 12,124 feet per 

 ton, and 15,600 feet per chaldron. The heat generated by the com- 

 bustion of tar and water, although much more intense than that 

 arising from ordinary fuel, may nevertheless be regulated at pleasure. 

 It is moreover uniform in its effects, a point which can only be ap- 

 preciated by the practical gas-maker. Let it not be inferred that the 

 exalted temperature exhibited in this process depends simply on the 

 entire combustion of the tar. Water, by its decomposition, affording 

 materials whose heating properties are inconceivably more energetic 

 than the ordinary kinds of fuel, and its elements combining readily 

 with carbon, it is easy to comprehend how these materials mutually 

 aid each other. The quantity or intensity of heat generated by a 

 VOL. in. 1834. E 



