1925. 
of Professor Leslie, for measuring ‘the 
intensities of the lights; Mr. Leslie’s 
instrument being affected by nori-tumi- 
nous ‘heat, Which tenders its indications 
much) less accurate than the former 
ingtrument, | 
_ Lo give even an abstract of the very 
long and able paper of Drs. C. and T. 
would be quite inadmissible, Mr. Edi- 
tor, in your miscellaneous columns ; 
-but a summiary of some of-the conelu- 
sions of these gentlemen may be wor- 
thy the attention of every person em- 
ploying gas for artificial lights. 
- From a vast number of trials, it ap- 
peared that the length of the flame has 
a most important influence in the pro- 
duction of light. For as the flame be- 
‘comes extended, its light increases in a 
much greater ratio than the expendi- 
“ture of gas. Thus, in a coal-gas jet 
burner, allowing for equal expenditures 
of gas, a two-inch flame giving a light, 
which may be called 100 degrees, a 
three-inch flame gave 109 ; a four-inch 
flame 131; and a five-inch flame 150. 
Beyond five inches, however, nothing 
is gained; on the contrary, the tip of 
the flame becomes darkened by a part 
‘of the gas passing off without being de- 
composed and consumed. It appears, 
‘therefore, that we obtain fifty per cent. 
more light from a coal-gas jet of five 
inches in height, than from one that is 
two inches high, with equal expenditure 
of gas; and the same proportion holds 
-good whether we use a :single jet, :or 
an Argand burner with numerous :aper- 
tures. . 
_ Now this fact alone tis certainly one 
of, the utmost importance, to the 
‘public as well as to the.gas companies 
generally. For it cannot be denied 
-that an immense waste of gas, or in 
other, words loss of light, must ensue 
from limiting the jet in our:street lamps 
to flame not more ‘than two dnches 
igh, and in some cases, the three jets 
exlled the “ cockspur burner,”: have:mot 
much more thanan inch offlame; above 
: orifice. It seems beyond a doubt, 
t the principles on which the com- 
bustion of gas for the purposes ofillu- 
aaination depends, have hitherto) been 
very little understood, even by :thase 
whose ‘business or profession renders 
it In @ manner incumbent ‘on them:to 
be masters of the whole subject. For 
the principles that govern the combus- 
tion of gas (and which are now for:the 
first time. fully developed, through the 
refined experiments and accurate ‘rea- 
soning ofithe able chemists before+men- 
Coal and Oi Gases compared. 
107 
tioned), are in themselves so obvious to 
every one moderately conversant with 
chemical science, as to” leave no doubt 
whatever with regard to the accuracy 
of the conclusions) drawn: by.thésé géh- 
‘tlemen’; ‘and which may be ‘bri 
stated thus :— 198 
If a gas flame of two inches‘in height, 
whether issuing from a single jet ora 
series of holes, be supplied with atmos- 
pheric air too rapidly, there will bea 
loss of illuminating -power in conse- 
quence. » For, although the light will 
-be vivid in such case, owing to.the 
copious supply of oxygen fromthe air.s 
yet the mass of .air from. whence* the 
oxygen is abstracted -bears so large a 
proportion’ to the volume of the flame, 
as to cool the exterior of the jet.of gas 
below the actual temperature of igni- 
tion, and will thus prevent its evolu- 
tion of light. Drs, Christison and: Pur- 
ner very justly corroborate the opinion 
of Sir H. Davy, with regard tothe ne- 
cessity of inflammable gas undergoing 
-decomposition immediately previous to 
its combustion, if we wish to have the 
full benefit of the inflammable substance 
in giving ott light and heat. eee) 
It has been satisfactorily shewn, b 
all the comparative experiments hitherto 
made.on carburetted hydrogen gas,.that 
the intensity of the light evolved is 
always nearly in proportion to \the:den- 
-sity of the compound gas—or, in other 
words, in proportion to the quantity of 
carbon in solution;in the hydrogen. It 
may be, therefore, clearly inferred, that 
{the illumination rom our artificial lights 
(whether gas, wax, oroil)-is-due to the 
‘union of the carbon with'the oxygenous 
‘portion of the air; and that the hydro- 
genvhas little agency .in the production 
.of light, beyond that-of being,the vehicle 
or menstrunm in whieh the -earbon jis 
wxetained in a gaseous |form, -and ready 
for instant combustion. 
Not only the intensity of the light, 
but, the duration of the gas also, de- 
pends-eittirely_on ‘the quantity \of car- 
bon in suspension: as is sufficiently 
proved by the durability of ‘oil gas in 
“compatison with that of coal igasjrand 
‘the greater quantity of oxygen required 
for:consuming)equal portions<of oil.gas 
and.:coaligas. - 
Now, if we .opem the stop-coek ofia 
gas-light which is burning at:two inches, — 
so as :to. extend the flame to four or 
‘five inches,.we obviously. gain two ,au- 
vantages :-1. ‘That the greater volume 
ef -flame givesa .greater i¢levation -of 
‘temperature for the decompositionapd 
P 2 - penfeat 
