346 TRANSACTIONS OF THE AMERICAN INSTITUTE. 



Magnesium produces one of the most intense lights that we have. Tt is 

 only necessary to light the end of a very small wire of* pure metallic mag- 

 nesium in an alcohol flame, when the wire is consumed, giving out a very 

 brilliant light. I have tried the experiment, but it is a disagreeable one tc 

 perform, on account of the effect of the light upon the eyes. It is some 

 time after looking at the magnesium flame before the eye is able to see 

 ordinary objects in a room. The experiment should not be tried without 

 providing protection for the eyes. The light in this case comes from the 

 oxyd of magnesium. The metal combines rapidly with oxygen, generating 

 a heat which makes the oxyd formed, the magnesia, incandescent, and it 

 is this white hot magnesia that emits the light. The magnesium light 

 might be utilized by winding a long wire of the metal upon a reel or bob- 

 bin, and unrolling the bobbin to feed forward the wire as it is consumed, 

 were it not for the high cost of the metal. It exists in large quantities, 

 especially in this country. At Hoboken there are deposits of porphyry 

 which contain magnesia, and in Westchester county are beds of dolamite, 

 composed to a large extent of magnesia. Magnesium is abundant; the 

 difficulty is to separate it from the oxygen and other substances with which 

 it is combined. 



Quicksilver is used to conduct a stream of electricity. 



Mr. Babcock. — I should like to hear the chairman's account of the Drum- 

 mond light. 



The Chairman. — I spoke of that in passing. It is very improperly called 

 the calcium light — there is no calcium in it except as lime, the oxyd of cal- 

 cium. The oxyhydrogen light is formed, as you are probably all aware, by 

 heating a bit of lime in the flame of the oxyhydrogen jet. The lime must 

 be chemically pure, and it is consequently necessary to prepare it for the 

 purpose. It is precipitated from a solution, and thus obtained free from 

 silica or any other substance. It is then pressed in a powerful hydraulic 

 press, in order to make it hard enough to be sawed into pieces of suitable size. 

 Lime is used because it cannot be fused, and under the intense heat of the 

 oxyhydrogen jet, it gives out the brilliant light with which you are familiar. 



The oxyhydrogen flame is formed by burning pure hydrogen gas in pure 

 oxygen. The gases are retained in separate vessels, and are mixed just 

 as they issue from the pipes. The hydrogen pipe surrounds that which 

 conducts the oxygen, and the oxygen pipe is now made to protrude a very 

 little beyond the end of the hydrogen pipe. This is the latest improvement 

 in the oxyhj^drogen light. 



Dr. Stevens. — The chairman forgot to mention one substance in his list 

 of illuminating materials — bayberry tallow This is used to a considerable 

 extent It is a vegetable tallow, produced by the bayberry bush. 



Mr. Stevens. — The Balm of Gilead tree produces a tallow which has been 

 collected and made into candles. Each bud has a small quantity of tallow, 

 and if the buds are placed in hot water, the tallow is melted, and may be 

 skimmed from the surface. I have collected a very little of this myself, 

 and I have heard my mother say that she and her mother collected one 

 year enough to serve for light for several months. 



The Chairman. — Will Prof. Seely give us the chemistry of illuminating 

 materials ? 



