i88 3 .] 
On Artificial Light . 
73 
is here a practical fallacy. The light, e.g., of a candle or a 
lamp is thrown full upon the objects to be illuminated, 
leaving the rest of the room comparatively obscure. Gas, 
except when conveyed by means of a flexible pipe to a mov- 
able table-burner, is burnt in the upper part of the room, 
and illuminates the ceiling and the walls quite as much as 
the books, papers, &c., on the table for which it is chiefly 
wanted. It is doubtless true that for i \d. we may obtain as 
much light with gas as we could with colza oil burnt in a 
solar lamp for 2f d. But if, as is generally the case, we have 
to produce at least three times as much light with gas as 
with an oil-lamp, in order to read or work with equal ease, 
the economy disappears. I think the experience of every 
man who has introduced gas into his house will be that he 
is out of pocket by the change. He obtains more light than 
he did from lamps, but not where it is most wanted. 
Another defeat of gas as a source of light is its unsteadi- 
ness. Theoretically it may be, perhaps, possible to make 
gas burn with a perfectly steady flame ; practically speaking 
this desideratum is not reached. If the flame of a gas-jet, 
of whatever -construction, is carefully watched it will be 
found constantly flickering. The effects of this unsteadiness 
are, in the long run, exceedingly irritating to the eye. 
A third, and perhaps more important, shortcoming lies in 
the products of the combustion of gas, which are of course 
emitted into the atmosphere of the room. Among these 
must rank sulphurous acid, which in contact with the moisture 
of the air passes gradually into sulphuric acid, and has an 
injurious aCtion upon pictures, wall-paper, the bindings of 
books, &c. Ethylene is probably never entirely absent 
among the products of the combustion of gas. The amount 
of watery vapour and carbonic acid is also excessive. Hence, 
except there is special provision for ventilation at the level 
of the ceiling, the atmosphere of a room lighted brilliantly 
with gas becomes most oppressive, and persons much ex- 
posed to it suffer from headache and languor. This is the 
case with visitors to our theatres, few indeed of which are 
even tolerably ventilated. Still worse is it the case with the 
assistants of certain drapers, &c., who are obliged to work 
by artificial light every evening save Sunday from 4 to g, 10, 
and in some cases even 11 p.m. The nature of the atmo- 
sphere in these shops may be guessed from the quantity of 
moisture which may be seen runnning down the insides of 
the window-panes on a cold evening. The carbonic acid 
given off must reach a correspondingly abnormal pro- 
portion. 
VOL. v. (third series). g 
