1883.] On Artificial Light. 75 
tearing up streets and wrecking houses — even to the east 
side of Tottenham Court Road. 
I may therefore sum up the defeats of gas-light as in- 
cluding unsteadiness of flame, emission of products of com- 
bustion harmful to persons and property, production of high 
temperature in upper parts of rooms, and danger of leakage 
or escape, whilst at the same time the commonly alleged 
economy of gas is in practice doubtful, or at most very 
slender. 
Hence it is evident that coal-gas as a source of light is 
very far from perfect. It appears, also, that its defects are 
of a nature not to be readily overcome or avoided by any 
improvement in its manufacture or mode of supply and con- 
sumption. It is scarcely conceivable that gas can be purified 
in such a manner as to be absolutely free from sulphur. 
Still less can it be rendered non-explosive when mixed with 
common air or compelled to burn with the absolute steadi- 
ness of a well-construCted lamp. 
I turn now to another great step in the production of arti- 
ficial light — the introduction of the mineral oils. These 
oils, when burnt in proper lamps, have certain advantages 
as well as defects. They are much more economical than 
refined vegetable oils, and give a brighter light than coarser 
seed or fish oils. They are probably in practice cheaper 
than gas, since they produce the light where it is wanted, 
and not in the upper part of the room. They are free from 
sulphur, and hence do not injure textile goods, books, furni- 
ture, pictures, &c. Otherwise their products of combustion 
are little different from those of gas. Being generally 
placed on tables, &c., they do not overheat the upper part 
of the room. 
But to balance these good properties come defects which 
cannot be ignored. Like all lamps, they are much more 
troublesome than candles or gas-jets. They must be cleaned, 
trimmed, and supplied with oil by daylight, and can never 
be safely replenished whilst burning. If inferior qualities 
of oil are used explosions of a serious nature may happen. 
The glass chimneys are liable to break if imperfectly an- 
nealed, or damp, or if the flame is turned up too suddenly. 
The overturning of a lamp — a not impossible occurrence- 
may easily give rise to a conflagration. Nor can such lamps 
be safely turned down if for the time being a good light is 
superfluous, for when burning dimly the products of their 
combustion are exceedingly unwholesome. To sleep with a 
petroleum lamp in the bed-room, turned down to a mere 
speck of light, may prove fatal. Hence mineral oil, though 
