362 



SCIENCE. 



[N. S. Vol. IX. No. 219. 



Dr. W. H. Birclimore* has devised an 

 apparatus for firing gaseous mixtures whicli 

 shows many of those phenomena. He uses 

 two large bulbs connected by a tube of de- 

 termined dimension for his exj)losion 

 chamber and a large tin foil condenser for 

 igniting the mixture, and he finds the phe- 

 nomena to be different from those observed 

 in tubes ignited in the ordinary way. The 

 reaction takes place more promptly and 

 sharply, and when using hj^drogen and air 

 in variable amount not only is some of the 

 oxygen ozonized, but hydrogen dioxide is 

 produced with the water of the reaction. 



When using acetylene, with sufficient air 

 to consume it theoretically, some of the 

 carbon is sepai-ated out in the solid form, 

 although free oxygen was found in the resi- 

 dues, and it was not until he had reached 

 eight times the volume of air required by 

 the theory that he got the theoretical amount 

 of carbon dioxide. 



He also describes a form of experiment 

 which very cleverly illustrates the succes- 

 sive phenomena occurring in the acetylene 

 explosion at Paris. 



The minimum volume of an inflammable 

 gas which forms an explosive mixture with 

 air is very considerably reduced if fine dust 

 is present in the air. Buddie directed at- 

 tention some 90 years ago, in an account of 

 the Wallsend Colliery explosion, to the 

 destructive effect produced by the ignited 

 coal dust at a distance from the point of 

 first explosion. Kobert Bald, in 1828, 

 pointed outf that the blast of flame from a 

 fire-damp explosion might ignite the coal 

 dust on the floor of the pit. Faraday and 

 Lyell, in theil- report on the Haswell Col- 

 liery explosion of September, 1844, J demon- 

 strated that coal dust may be instrumental 

 in greatly extending and in increasing the 

 disastrous effects of fire-damp explosions. 



* Am. Gas Light J. 67, 563-565 ; 1897. 

 fEd. Phil. J. 5, 101; 1828. 

 t Inst. C. E. Tracts, vol. 284. 



Abel* has shown that the presence of finely 

 divided incombustible mineral matter in air 

 containing less than 2 per cent, of fire damp 

 causes the latter to become explosive on igni- 

 tion, and Gallowajr has proved that a mixture 

 of air containing less than oneper cent, of fire 

 damp can be made to explode when charged 

 with fijieljf divided coal dust. I have applied 

 this observation of the effect of the dust in 

 facilitating explosions to lecture experiments 

 with inflammable gaseous mixtures, f 



The explosion at the Capitol on Novem- 

 ber 6th was confined to that portion of the 

 building known as the. Supreme Court 

 section and which joins the Senate wing to 

 the central structure. In the center of this 

 section is a dome which is rarely noticed, 

 as it is completely overshadowed by the 

 central dome of the Capitol. This dome is 

 supported in the sub-basement on piers, 

 while all about these j)iers are brick vaults 

 and arches of varying heights, carrjdng the 

 many partition walls and floors above them, 

 and these, with those radiating from under 

 the big dome and the connecting passages, 

 form a perfect labjainth. The complexity 

 is increased by several of the spaces having 

 been enclosed with brick walls so as to carry 

 steam-heating coils and for other purposes. 

 A large part of the wall space had been 

 fitted with shelving, and these were filled 

 to overflowing with pamphlets. One space 

 was used as an engine room, from which to 

 operate a Sturtevant blower that fed air 

 over the coils. This engine was provided 

 with a woven guard screen to protect 

 j)assers-by, made from 5/16-inch wi'ought- 

 iron rods, riveted on each edge into two 

 ^^fl■ought-iron bars, each of which was 7/8 

 inches wide by 7/16 inches thick. Directly 

 opposite this screen and leading south was 

 a low, narrow passage that opened into one 

 of the largest and highest of the vaults, in 

 which was stowed, in the open spaces be- 



* Accident in Mines, Proc. Inst. Civ. Eng., 1888. 

 fProo. U. S. Nav. Inst. 12, 4'29 ; 1886. 



