lamps. The standard of illumination adopted for the table is one which is
only gaining general recognition where incandescent gas or acetylene
lighting is available, though in exceptional cases it has doubtless been
attained by means of oil-lamps or flat-flame gas-burners, but very rarely
if ever by means of carbon-filament electric glow-lamps, or candles. It
assumes that the occupants of a room do not wish to be troubled to bring
work or book "to the light," but wish to be able to work or read
wheresoever in the room they will, without consideration of the
whereabouts of the light or lights.

It should, perhaps, be added that so high a price as 5s. per 1000
cubic feet for coal-gas rarely prevails in Great Britain, except in small
outlying towns, whereas the price of 6d. per Board of Trade unit
for electricity is not uncommonly exceeded in the few similar country
places in which there is a public electricity supply.



CHAPTER II

THE PHYSICS AND CHEMISTRY OF THE REACTION BETWEEN CARBIDE AND WATER

THE NATURE OF CALCIUM CARBIDE.--The raw material from which, by
interaction with water, acetylene is obtained, is a solid body called
calcium carbide or carbide of calcium. Inasmuch as this substance can at
present only be made on a commercial scale in the electric furnace--and
so far as may be foreseen will never be made on a large scale except by
means of electricity--inasmuch as an electric furnace can only be worked
remuneratively in large factories supplied with cheap coal or water
power; and inasmuch as there is no possibility of the ordinary consumer