1853.] OF THE ROYAL INSTITUTION. 323 
shews that a normal gas for illuminating purposes should consist of 
illuminating hydrocarbons diluted with pure hydrogen. No method 
is known by which a gas of exactly this composition can be manu- 
factured, but a very close approximation has been lately made to 
this normal gas, by the employment of a process known as White’s 
Hydrocarbon method of gas-making. In this process the very 
ingenious principle is adopted of generating the illuminating con- 
stituents in as concentrated a form as possible in one retort, and 
the diluents consisting principally of hydrogen free from light- 
carburetted hydrogen in another. By this arrangement the diluents 
can be employed for a very remarkable and highly interesting 
purpose; they are conducted through the retort in which the illu- 
minating constituents are being generated, in such a manner as 
rapidly to sweep out those constituents, before they have time to 
become decomposed by contact with the red hot interior surfaces of 
the retort, a mode of destruction which occurs so largely in the 
usual process of gas-making. This mode of treatment produces 
a gain in the amount of illuminating power derived from a given 
weight of coal, equal to from 50 to upwards of 100 per cent, whilst 
the increase in quantity of gas is frequently 300 per cent. 
The gas thus manufactured differs principally from coal gas made 
by the ordinary process, in having a large portion of the light 
carburetted hydrogen replaced by hydrogen; it is therefore in a 
sanatory point of view the best gas hitherto produced. This is 
seen in the following Table, which exhibits the amount of carbonic 
acid and heat generated per hour by various sources of light, each 
equal to 20 sperm candles burning at the rate of 120 grains of 
sperm per hour. 
Carbonic Acid. Heat. 
Tallow - - 10.1 cubic feet 100 
Wax one ics ‘ 8.3 hander 82 
Spermaceti - - 
Sperm Oil (Carcel’s Lamp) 6.4 ey he 63 
London Gases, B, C, D, E, 5.0 5 > 47 
Manchester Gas - 4.0 rr 3 32 
London Gas, A. 3.0 ‘, e 22 
Boghead Hygnodackion Gas 2.6 ps a 19 
Lesmahago ‘Hydrocarbon Gas 2.5 rr e 19 
Notwithstanding the great economy and convenience attending 
the use of gas, and, in a sanatory point of view, the high position 
which, as an illuminating agent, coal gas of proper composition 
occupies, its use in dwelling houses is still extensively objected to. 
The objections are partly well founded and partly groundless. As 
is evident from the foregoing table, even the worst London gases 
produce, for a given amount of light, less carbonic acid and heat 
than either lamps or candles. But then, where gas is used, the 
consumer is never satisfied with a light equal in brilliancy only to 
