this process, which of itself is a disagreeable one, reaches several
hours every day. Habit has taught the country dweller to accept as
inevitable this waste of time, and largely to ignore the odour of
petroleum in his abode; but the use of acetylene entirely does away with
the daily cleaning of lamps, and, if the pipe-fitting work has been done
properly, yields light absolutely unaccompanied by smell. Again, unless
most carefully managed, the lamp-room of a large house, with its store of
combustible oil, and its collection of greasy rags, must unavoidably
prove a sensible addition to the risk of fire. The analogue of the lamp-
room when acetylene is employed is the generator-house, and this is a
separate building at some distance from the residence proper. There need
be no appreciable odour in the generator-house, except during the times
of charging the apparatus; but if there is, it passes into the open air
instead of percolating into the occupied apartments.

The amount of heat developed by the combustion of acetylene also is less
for a given yield of light than that developed by most other illuminants.
The gas, indeed, is a powerful heating gas, but owing to the amount
consumed being so small in proportion to the light developed, the heat
arising from acetylene lighting in a room is less than that from most
other illuminating agents, if the latter are employed to the extent
required to afford equally good illumination. The ratio of the heat
developed in acetylene lighting to that developed in, _e.g._,
lighting by ordinary coal-gas, varies considerably according to the
degree of efficiency of the burners, or, in other words, of the methods
by which light is obtained from the gases. Volume for volume, acetylene
yields on combustion about three and a half times as much heat as coal-
gas, yet, owing to its superior efficiency as an illuminant, any required
light may be obtained through it with no greater evolution of heat than
the best practicable (incandescent) burners for coal-gas produce. The