534? Dr. R. Hare on the Explosiveness of Nitre, 



nitre and combustibles were brought into collision for the last 

 time, at which the finishing explosion took place, has oc- 

 curred, than that of comparing it with the blow by which 

 nitre and sugar were exploded, as above mentioned, in one 

 of my experiments. 



The weight of the combustible matter contained within the 

 store was 700,000 pounds. The store was 90 feet deep by 

 24 wide. Supposing the horizontal area of the sledge, as ap- 

 plied, to have been 3x3 = 9 square inches, it seems that for 

 every equivalent horizontal area within the store, there must 

 have been twenty-two pounds, or about three times the weight 

 of the sledge. Hence, in descending from a height of 20 or 

 30 feet, which there was ample room for it to reach, the com- 

 bustible congeries may have attained a much greater velocity 

 than could be imparted to the sledge, and may consequently 

 have produced a much more forcible impact. At the same 

 time, this must have caused an intimate penetration and in- 

 tensity of compression, which by a dead weight it is almost 

 impossible to create. 



This explanation, so far as it rests upon the assumption 

 that the combustibles were made to dance upon the surface 

 of the melted nitre, is supported by the fact, that any combus- 

 tible mass, when thrown upon the surface of incandescent 

 nitre, will undergo a dancing motion, so as sometimes to leap 

 out of a deep pot within which the experiment may be made. 



18. The phaenomena are not irreconcilable with the idea 

 that some of the earlier explosions arose from the falling of the 

 liquid nitre upon the combustibles before all the floors gave 

 way ; but it should be recollected that nitre fuses at a low red 

 heat, and at a cherry-red gives out oxygen gas. The pre* 

 sence of this gas, as well as the deflagration resulting from 

 contact with the liquid nitre, must have caused the floors to 

 be oxidized with a rapidity far exceeding that which takes 

 place during ordinary conflagrations*. To the causes of 

 quick destruction thus suggested, must be added the mecha- 

 nical force of the explosions directly at war with the per- 

 sistence of the floors. That, prior to the last explosion, the 

 nitre must have been collected in the cellar, may be assumed 

 from the fact, that the temperature being inevitably far above 

 its fusing-point, the salt must have been all liquefied, and oc- 

 cupying the lowest accessible cavity, on account of its supe- 

 rior specific gravity. This assumption is moreover justified 

 by the circumstance that the force of the explosion appears to 

 have been especially exerted upon the parietes of the cellar, 



* See Note to paragraph 9, pages 528, 529. 



