248 



MR. J. LEIGH ON THE GAS 



evident that the tar and water gas really contained no defiant 

 gas whatever ; and that even the low illuminating power 

 which it seemed to possess, when tried by the photometric 

 test at the station where it was manufactured, was due to a 

 little naphtha vapour which the gas held in mechanical sus_ 

 pension, and had not had time to deposit; whilst the sample 

 I analysed, having been retained in a cool place for a time, 

 had allowed of this deposition. Of course, if this gas had 

 been sent into the town, the whole of the naphtha vapour 

 would have been deposited in the pipes. 



Another very remarkable fact is the entire absence of 

 carbonic oxide in the gas, whilst this exists in the other 

 two samples of gas, the analysis of which is quoted in the 

 proportion of 4'8-i and 10*10 respectively. If the water in 

 these experiments had been in the slightest degree decom- 

 posed by the tarry matters, or even by the pitchy residue, 

 carbonic oxide would have been one of the products. 



What really took place in the process is now sufficiently 

 simple. The naphtha from the tar, distilled over at once, 

 and condensed in the gas-holder after a time, but a little 

 remained dissolved or suspended in the gas for a brief 

 period. 



The less volatile portion of the tar decomposes, and is 

 converted into light carburetted hydrogen and hydrogen. 

 The large proportion of the latter would seem to show, that 

 a small portion of the water employed in the process is de- 

 composed by the iron of the retort rusting the latter, and 

 yielding hydrogen. 



The nitrogen in the gas proceeds from atmospheric air, 

 and not from the materials employed. 



Now the elements of tar are the same, but in different 

 proportions, as those of resin, and exist in a state quite as 

 fit to enter into combination with those of water ; and these 

 experiments prove infinitely better than an analysis of the 

 resin gas itself even would do, that in the manufacture of 



