September 10, 1886.] 



SCIENCE. 



231 



— Glanders is said to be quite prevalent among 

 horses at the present time. The Nevv York state 

 board of health has discovered six cases at Middle- 

 town. 



— The Paris Conseil municipal has ceded to the 

 Society of the Institut Pasteur for ninety-nine 

 years the gi'ound upon which the institute is built. 

 The following official statement has just been 

 made : The whole number of persons treated by 

 Pasteur is 1,656 (of these, 15 have died) ; 1,009 of 

 these were French (3 of them died) ; 182, includ- 

 ing 50 bitten by rabid wolves, were Russians (3 of 

 these bitten by dogs, and 8 by wolves, have died) ; 

 20 were from Rouniania, with one death ; of the 

 others, 59 were from England, 17 from Austria, 

 74 from Algeria, 18 from America, 2 from Brazil, 

 42 from Belgium, 58 from Spain, 7 from Greece, 

 8 from Holland, 25 from Hungary, 105 from Italy, 

 20 from Portugal, 2 from Turkey, and 2 from 

 Switzerland (of all these, not one has as yet died : 

 the total mortality, therefore, is less than one per 

 cent, — a most striking commentary upon the 

 views of those who declare Pasteur's methods a 

 failure). 



— At the last meeting of the American associa- 

 tion, Eugene Michel Chevreul, on the motion of 

 the section of chemistry, was elected an honorary 

 fellow, the second only on the rolls of the associa- 

 tion. 



LETTERS TO THE EDITOR. 



*t* Correspondents are requested to be as brief as possible. The 

 writer's name is in all cases required as proof of good faith. 



Dynamite explosions. 



In its issue of the first insfc. , ref erring to the recent 

 Chicago explosion, the New York Herald publishes, 

 under the heading ' Teachings of the explosion,' an 

 article containing ' some things ' claimed to be ' in- 

 structive and important,' but which are so incorrect 

 as to be neither. In this article it says, "But we 

 know now, happily at the cost so far of but two 

 human lives, some things that are instructive and im- 

 portant. One is, that a huge mass of dynamite, say 

 ten tons, even when blended with five times its weight 

 of gunpowder, expends its main force downward, 

 thus verifying, on a vast scale, a fact known of the 

 explosion of much smaller quantities of dynamite. 

 Another fact is, that dynamite, even in huge volumes, 

 is less likely to ignite neighboring masses of explosives 

 in such a casualty than an unmixed mass of gun- 

 powder would be. There were ten large magazines 

 close to the Laflin & Rand, and all escaped ignition." 



The above statement, that ' a huge mass of dyna- 

 mite,' in exploding, ' expends its main force down- 

 ward,' and the deduction that this verifies, "on a 

 vast scale, a fact known of the explosions of much 

 smaller quantities of dynamite," are so scientifically 

 inaccurate as to need correction. The fact is, dyna- 

 mite explodes with equal force in all directions, and 

 that, at whatever point it meets with the greatest 



resistance, at that point it is most destructive, 

 whether it is upward, downward, or laterally. 



It is a common error, however, that dynamite 

 always ' expends its main force downward,' which 

 arises, probably, from the fact that, in the majority 

 of reported dynamite explosions, it has met with the 

 greatest resistance from the earth, and therefore has 

 exhibited its ' main force ' in that direction. 



Mr. G. M. Roberts, manager of the Nobel's explo- 

 sives company, London, writes as follows to the Lon- 

 don^ Times.* " Nitroglycerine and dynamite do not, 

 when exploded, exert such a force as is popularly be- 

 lieved. To speak precisely, the power developed by 

 the explosion of a ton of dynamite is equal to 45,675 

 tons raised one foot, or 45,675 foot tons One ton of 

 nitroglycerine similarly exploded will exert a power 

 of 64,452 foot tons ; and one ton of blasting gelatine, 

 similarly exploded, 71,050 foot tons. These figures, 

 although large, are not enormous, and need not excite 

 terror. Seventy-one thousand tons of ordinary build- 

 ing-stone, if arranged in the form of a cube, would 

 measure only 90 feet on the side, and, if it were pos- 

 sible to concentrate the whole force of a ton of blast- 

 ing gelatine at the moment of explosion on such a 

 mass, the only effect would be to lift it to the height 

 of a foot. The foregoing figures are derived from 

 experiments made at Ardeer with an instrument 

 which gives accurate results in measuring the force 

 of explosives." 



Supposing these data to be reliable, and in view of 

 the fact that the buildings which stood on the great 

 excavation in Chicago have disappeared entirely, is 

 it not reasonable to suppose that fully as much force 

 was required to lift, splinter, and distribute, in every 

 direction, the materials composing those buildings, 

 overcoming the attraction of gravitation in the act, 

 as was necessary to make the great excavation in 

 the earth, by the expenditure of ' its main force 

 downward' ? 



This fact of the elimination of the buildings seems 

 to have escaped the notice of the writer of this article. 



In verification of our statement that it explodes 

 with equal force in all directions, the following ex- 

 tract from the above quoted authority, Mr. Roberts, 

 is cited: "I have often, by way of experiment, 

 exploded a pound of dynamite suspended fi'om the 

 end of a fishing-rod by a string about six feet long, 

 holding the rod in my hand the while. As there was 

 no solid matter to project, I received no injury, and 

 the end of the fishing-rod was not even scratched. 

 About three feet of the string at the end of the rod 

 was always left uninjured." 



Meeting, in the above experiment, with no resist- 

 ance other than the air at any point, there was con- 

 sequently no destructive power shown in any direc- 

 tion ; but, had there been solid matter above or below 

 or on either side, the ' main force ' would have been 

 expended upward or sideways, and not 'downward.' 



This experiment illustrates another remarkable 

 feature in dynamite, peculiar to itself, — that of its 

 concentrated or local effects, compared with the more 

 diffused effects of gunpowder explosions. 



Quoting again from Mr. Roberts, he says, " The 

 power exerted by an explosion on surrounding objects 

 is in the inverse ratio of the cube of the distance from 

 the point of explosion. Thus, at 100 feet from the 

 exact point of an explosion, the power is only the cube 

 of 1-100 or 1-1,000,000 part of what it is at a distance 

 of only one foot from that point, or, in other words, 

 if the power at one foot from the spot be represented 



