201 
LIGHT. 
sica oleracea arvensis of De Candolle, and it has lately been 
found that the sulphur contained in this seed was dissolved 
in the gas, and had a pernicious effect on the neighbour 
hood where it was consumed. The gas attacked metallic 
substances and affected respiration. The brass burners were 
soon corroded and destroyed, and filled with an efflores 
cence, which has been analyzed and shown to be a sulphate 
of zinc and copper, a sub-sulphate of copper, phosphate of 
copper, and oxide of iron, with some accidental traces of 
silica. This shows the necessity ofwashingthegas thoroughly, 
and of not using these seeds, if the washing will not clean 
the gas. 
In consequence of oil gas giving, in proportion to its 
bulk, a much greater quantity of light than coal gas, it has 
been compressed into strong iron vessels, casily portable, 
and our houses and drawing rooms may now be illuminated 
by lamps that never need snuffing, sputter no grease, spoil 
no clothes, make no dirt, and never give a single spark. 
They may be carried about without danger, and if turned 
over or let fall, neither spill oil nor tallow. In general, 
they are not yet adopted, because people adhere to old prac 
tices and hate novelties ; but ultimately they well come into 
use, and we shall be saved both dirt and trouble, and risks 
of fire will be diminished. In the lamps with which the 
London portable gas company engage to supply their cus 
tomers, the gas is compressed into 1/32 of its usual volume. 
It has been customary to consume oil gas with the same 
sort of burners as coal gas, which causes a considerable 
waste, and gives rise to a mistaken idea of the quantity of 
light given out by each gas. The argand burner, which 
admits the gas through a number of small holes, is the best 
species for perfect combustion, but, which would hardly 
have been imagined, it is found that these holes should be 
nearer together and smaller for oil gas than for coal gas. In 
any case they should be only so far apart that the flame from 
cach should just coalesce with that from the next. The gas 
produced from oil contains more carbone than that from 
coal ; the light is in proportion to the quantity of carbone, 
and the same sized holes which completely consume the 
carbone of the coal gas do not burn all that of the oil gas. 
It is, consequently, necessary that burners for oil gas should 
be made with smaller holes, and these holes should be 
closer together than those for coal gas. Hence oil gas is 
unfit for street lamps, as it is much more liable to be blown 
out by the wind.