200 SECONDARY PRODUCTS. 



was found to give the timber a considerable degree of hardness, but not of 

 durability. Its smell is extremely offensive, and at the present time is used 

 only in places where that is of no consequence. The exposed part of the 

 machinery of a gas establishment may be protected by being coated with 

 coal-tar. 



Another product obtained by the distillation of coal-tar was a peculiar oily 

 naphtha, which burned with a very bright flame. It was used as a substitute 

 for whale-oil in the lamps on Waterloo Bridge and its neighbourhood in 1819 ; 

 but unless copiously supplied with atmospheric air, and kept with a small 

 flame, the quantity of carbon it deposited was excessive ; the gas supplying 

 the flame being almost entirely bi-carburetted hydrogen, which requires at 

 least three times its bulk of pure oxygen for its complete combustion, and 

 consequently fifteen times its volume of atmospheric air. 



If coal-gas is conducted through this naphtha before being burned, the light 

 is increased in brilliancy more than fifty per cent. I witnessed an experiment 

 of this at Mr. Lowe's house a few weeks ago, and certainly the effect was 

 dazzling. The naphtha was contained in a sponge placed in an air-tight cup 

 or vase below the burner. Mr. Lowe has also obtained this increase of illumi- 

 nating power by filling the meter with naphtha, and thus describes his 

 method : 



" As regards the first part of the same in increasing the illuminating power of such 

 coal-gas as is usually produced in gas-works, by impregnating such gas with naphtha, 

 commonly called spirit of coal-tar, or with any other volatile hydro-carbonaceous liquid : 

 the method I adopt for so impregnating the said gas is by merely filling the case of 

 the common gas-meter to the usual height with any of the said liquids instead of water, 

 by which means the said gas discharged by the meter to the burners, is, during the ope- 

 ration of measuring, sufficiently impregnated with the said liquid in the meter-case. 



It is important to maintain a proper and uniform supply of such liquids in the 

 meter-case, and this may be effected by means of any self-acting apparatus, such as the 

 bird-fountain." 



To ensure the separation of the richer naphtha during the condensation of 

 coal-gas, Mr. Lowe, in another part of his specification, proposes to turn 

 steam into the upper portion of a long inclined pipe, through which the gas 

 passes on its way to the purifiers. The vapours of the water and bitumen 

 have a mechanical affinity for each other, and will fall together at several 

 points in the condensing-pipe : for the purpose of conducting them away, 

 syphons are attached at the proper places. The contents of the last or lowest 



