37S 



Scientific Inielligence^ 



ITJOutli of a large apparatus for distilliog coal entered into this 

 room, so that it was kept constaiitly filled with the vapour of 

 coal tar, and carbureted hydrogen gas. By the heat of the 

 room the water was slowly expelled from the wood, and the 

 empyreumatic oil from the coal took its place. By this con- 

 trivance the wood was not only thoroughly driedj but was pre- 

 vented from again imbibing water by being soaked with oil. It 

 is obvious that the air of the room would be a mixture of the 

 inflammable gas from oil and the common air. Now we learn 

 from Dr. Henry's experiments that the medium specific gravity 

 of the gas from coal is scarcely equal to i that of common air* 

 For complete combustion it requires scarcely so much as twice 

 its bulk of oxygen gas. The result of my experiments was, that 

 it would not burn unless it amounted to rather more than -jVth 

 of the common air with which it was mixed. For complete 

 combustion it would require about nine times its bulk of common 

 air; but I believe that complete combustion never takes place in 

 such mixtures. 



These fects are sufficient to account for the explosion at 

 Woolwich. We have only to suppose that the inflammable gas 

 in the room exceeded -j-Vth of the common air. There was a 

 flue that ran along the floor of the room. Somehow or other the 

 flame must have issued through this flue at the moment the 

 damper was applied at the top of the building; for the explosion 

 took place just at that instant. The first combustion would be 

 imperfect ; more common air w'ould rush in immediately after 

 the first explosion ; and this new mixture, kindled in the same 

 way as the first^ produced the second explosion. It is needless to 

 say that the house was completely demolished. Nine men were 

 unfortunately killed. The explosion was precisely similar to 

 what happens so frequently in coal-mines ; a very dismial example 

 of which will be found in a preceding part of this number of our 

 Annals. 



IL New Properties of Light: 

 In our last number we gave an account of some of the curious 

 discoveries respecting light lately made by the French philoso- 

 phers, ^ and by Dr. Brewster in this country. W^e shall now 

 finish what we liave farther to say on that subject. Dr. Brewster 

 ijonfirmed Sir Isaac Newton's conjecture that the colours pro-^ 

 duced by heat upon the surface of polished steel are owing to a 

 thin glassy transparent film of oxide, of various thickness, cooling 

 the surface of the steel; for he found the light reflected from 

 this furface at a certain angle polarized, while the light from the 

 surface of the steel itself was not polarized. Dr. Brewster 

 found, contrary to the assertion of Malus, that light suffers 

 some modification by reflection from metallic surfaces. He 



