NATURAL PHILOSOPHY. 137 



sion, the zircon adheres to the other substances, and burning adds 

 to the solidity of this adhesion. The crayons are made in the 

 same manner as those of magnesium.— F.MoiGNO, in Journal of 

 franklin Institute^ August, 1868. 



THE MAGNESIUM LIGHT. 



The light emitted by a magnesium wire one-thousandth of an 

 inch in diameter, is equal to that of 74 stearine candles, of 5 to the 

 pound ; 3 feet of it are burned per minute, or a quarter of an 

 ounce per hour, the cost of which, at the present price, would be 

 about 2s. 6d. Seventy-four stearine candles would, however, in 

 the same time consume 2 pounds of stearine, which would cost 

 2s. ; 40.4 cubic feet of 12 candle coal gas would be required 

 to produce the same effect, and would cost about 2|d. The dear- 

 ness of magnesium arises from the dearness of sodium required 

 in obtaining it. Magnesium gives off 265 times less heat than 

 gas. Gas and candles vitiate the air by the production of watery 

 vapor and carbonic acid. Magnesium is free from this objection, 

 but it has an inconvenience of its own : a large quantity of calcined 

 magnesia is thrown off as a fine powder, which soon renders the 

 atmosphere of a room intolerable. This is also objectionable in 

 photography, though used for very short periods. At best, mag- 

 nesium can be only an imperfect substitute for sunlight ; its light 

 has been found to be only the 4.525th of that of the sun on a 

 bright November dav, but at the same time its chemical effect was 

 ascertained to be the 1.36th of that of the sun. 



CARBURETTED COAL GAS. 



At a recent meeting of the Massachusetts Institute of Technol- 

 ogy, Mr. 0. P. Sykes exhibited, in operation, his apparatus for 

 carburetting the ordinary street gas, thereby, as he claimed from 

 his experiments, diminishing by about 40 per cent, the amount 

 consumed, and at the same time increasing the light nearly one- 

 half. The carbonator is a strong sheet-iron box, with apartments 

 arranged so as so compel the gas to travel a considerable distance 

 to take up the vapor of the hydrocarbon, which fills it, and with a 

 stuffing of shavings of wood, such as are used in making the so- 

 called "Excelsior mattress." The light hydrocarbons of petro- 

 leum, of about 71 gravity, are employed in the apparatus. As no 

 air can gain admission to the boxes, which are securely locked, 

 the hydrocarbon vapor cannot become explosive. He stated that 

 1 gallon of the hydrocarbon will carbonize 1,000 feet of gas; 

 the cost of the apparatus, exclusive of the lead pipe and 

 change of burners, is from $15 to $20 for an ordinary dwelling- 

 house ; as the amount of gas consumed is much less with than 

 without the hydrocarbon vapor, the burners are reduced in size 

 one-half, and yet the amount of light is increased. He stated that 

 the incrustations which form in old gas-pipes, sometimes diminish- 



12* 



