The chemical constitution of this gazeous fluid is best ascertained by burning it in a vessel of oxygen gas, over lime-water in a pneumatic reservoir, by means of a bladder and bent brass pipe. Two products are then obtained, viz. water and carbonic acid. That water is produced, may be shown by burning a very small stream of the gas in a long funnel-shaped tube open at both ends. The formation of carbonic acid is evinced, by the copious precipitation of the lime-water in the foregoing experiment. If carburetted hydrogen be mixed with a sufficient quantity of oxygen gas or common air and fired by the electric spark, or by any other method, an explosion takes place more or less violent according to the quantity of carbonaceous matter condensed in the hydrocarbonat; and the remaining gas consists of carbonic acid, together with any unconsumed gas, or excess of oxygen, whilst the water condenses in drops on the sides of the vessel. A few cubic inches of the mixed airs is as much as can be conveniently managed at a single explosion; and when any portion of olefiant gas is present, even this quantity will endanger very thick glass jars. A very vivid red flame appears at the moment of the explosion, and a great enlargement takes place in an instant, after which the bulk is suddenly reduced to much less than the original quantity. When the carbonic acid is absorbed by lime-water, if the gasses have been properly proportioned, no gazeous residue is left, except accidental impurities. Though carburetted hydrogen gas, is sometimes naturally produced in coal-mines, and occasionally mixes with common air, producing dreadful explosions, yet when coal-gas is mixed with common air, it does not explode unless the gas be to the air as 1 to 10 nearly. Such are the leading chemical habitudes of this gazeous product. The varieties of carburetted hydrogen gas all agree in being inflammable; but they possess this property in various degrees, as is evinced by the variable brightness of the flame which they yield when set on fire. “Messrs. SOBOLEWSKY and HORRER, of St. Petersburgh, have employed wood for the purpose of producing carburetted hydrogen gas. The pyroligneous acid obtained in this operation, when freed from the empyreumatic oil with which it is mixed, becomes acetous acid, and is applicable to all the uses of vinegar. A cubic cord of wood equal to 2.133 French metres (a metre being rather more than an English yard), yields 255 Paris pounds of charcoal, and 70 buckets of acid. The latter gives 30 pounds of tar, after the extraction of it 50 buckets of good vinegar remain. The same quantity of wood furnishes 50,000 cubic feet of gas, sufficient for the supply of 4000 lamps for five hours.”[20] [20] See Repository of Arts, Vol. XI. No. 36, p. 341. UTILITY OF THE GAS-LIGHT ILLUMINATION, WITH REGARD TO PUBLIC AND PRIVATE ECONOMY.