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gas. It forms with oxygen a powerfully explosive mixture, 
when the volume of the latter is to that of the former, as 
three or four to one. The new gas explodes spontaneously 
when brought in contact with chlorine gas; and this effect 
is accompanied with the production of flame, and the copious 
deposition of carbon: and is quite independent of the action 
of light, or the sun’s rays, as it readily takes place in the 
dark. Under the ordinary pressure of the atmosphere, 
water absorbs about its own bulk of the gas, which is co 
liberated by heat, apparently unaltered. 
According to Professor Davy’s experiments, the new gas 
consists of a volume of hydrogen gas and two volumes of 
the vapour of carbon condensed into one volume; and it 
requires for its complete combustion two and a half volumes 
of oxygen gas. Its specific gravity is 0.917, that of common 
air being 1.000. 100 cubic inches of it weigh 28.4378 grains. 
The equivalent of the new gas appears to be 13.24, and 
the formula by which it is expressed is 2c+H, or c?-+-H. 
The name proposed for it is bicarburet of hydrogen, which 
simply expresses its chemical constitution. 
A paper by Professor Mac Cullagh, “ on the Properties 
of Surfaces of the second Order,” was read. 
Among various other matters, this paper contains a new 
class of properties which are analogous to the focal proper- 
ties of the conic sections. The author has found that sur- 
faces of the second order may be generated by means of a 
given point as focus, a given right line as directrix, and a 
given plane. In general, every such surface is the locus of 
a point, whose distance from the focus bears a given ratio to 
its distance from the directrix, the latter distance being 
measured parallel to the given plane. This mode of gene- 
ration, however, excludes surfaces of revolution about the 
major axis, as the corresponding generation of the conic 
sections excludes the circle. When the given ratio is not 
