84 
POPULAR SCIENCE REVIEW. 
The moderator is another form of lamp now in very common 
use. It involves two or three important principles, one con- 
sisting of a powerful spring, whose force is equal to from fifteen 
to twenty pounds, which presses on a disk and forces the oil up 
a tube, whence it flows over the burning wick, which is thus 
always saturated, as in the Carcel lamp. To prevent the oil, 
however, from flowing over too rapidly, there is placed in the 
tube an ingenious regulator, or moderator, of a tapering shape, 
winch is so contrived as to check and diminish the flow of oil in 
proportion as the pressure is increased, always allowing suffi- 
cient oil to pass to feed the lamp when burning. The oil, being 
thus supplied with perfect regularity, just saturates a hollow 
circular wick, through the middle of which a current of air is 
constantly drawn by means of a glass chimney. A number of 
small contrivances introduced by Argand, the inventor of the 
circular burner, have brought it to a state of extreme perfection. 
Common vegetable oils can be burned with advantage in lamps 
where the current of air is strong and where care is taken that 
the top of the wick is kept smooth; but all these oils are costly, 
and the quantity of smoke that arises from the unconsumed fuel 
is extremely disagreeable. Animal oils are not generally used, 
owing to the smell they emit when burning. 
Mineral oils are now entering into large consumption, and of 
these the recently-introduced paraffine oil is one of the most 
remarkable. It will be necessary to consider a little the nature and 
preparation of this curious substance, if we would fully under- 
stand the very great change that has taken place of late years 
with regard to the methods of obtaining artificial light. 
Paraffine, though only recently manufactured in sufficient quan- 
tity to be used practically, has been long since known as one of 
the products derived from a peculiar destructive distillation of 
vegetable matter, whether in the state of wood, peat, or coal. 
Various bituminous shales and other mineral deposits that abound 
in some parts of the world, also yield the same substance. It is 
obtained by carrying on the distillation in a retort kept at a low 
red-heat, the products being received and condensed at a 
temperature of about 55° Fahr. in a very carefully-contrived 
apparatus. A light oil is the principal result of this operation, 
and this oil, after being- purified and re-distilled, is found to be a 
fluid compound, containing- a certain proportion of paraffine oil, 
which greatly resembles clear transparent naphtha, a somewhat 
heavier oil, also used for burning, a lubricating- oil, and solid 
paraffine. The light oils yield an intense white light, admirably 
adapted for general use. 
In order to obtain a clear smokeless flame from paraffine oil, 
it is necessary to take some precautions. Owing- to the capil- 
lary action of the cotton used as a wick, the fluid oil may be 
