NATURAL PHILOSOPHY. 165 



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that one is more instantaneous than the other, without implying duration to 

 one at least, which also implies that it is not instantaneous. Xow, many of 

 the fulminating- powders, and even gun cotton, are, as is well known, fired 

 much more rapidly than gunpowder. The firing of this last cannot, therefore, 

 be instantaneous, and we might rest with this logical solution of the question ; 

 but, like many other logical solutions, it adds but little to our wisdom, and the 

 amazing rapidity with which a large mass of powder is inflamed, when hi a 

 close cavity, awakens our attention to the course of the events causing, or at 

 least accompanying, this inflammation, and I shall notice two experimental 

 results which seem to me to indicate the state of things during that whole 

 course. 



First. Count Rumford has proved that the burning of the grains is slow, or 

 that a sensible time is required with each gram before it is wholly converted 

 into the gaseous state ; and secondly, various experiments made in England 

 and in Prussia have shown that there is no sensible difference produced in the 

 velocity of the shot by communicating the fire to the centre rather than to one 

 end of the charge, which ought evidently to take place if the fire is commu- 

 nicated from one gram to another hi succession, as this communication, being 

 hi both directions, when proceeding from the middle, would require but half 

 the time that is required when proceeding from one end, and ought to produce 

 a sensible increase hi the velocity of the shot. I think, therefore, that these 

 two facts warrant the following inference as to the course of the action during 

 the production of the force. "When the fire reaches the charge from the 

 touchhole, the nearest grams become kindled ; the hot fluid evolved is thrown 

 further into the charge, and the burning succeeds successively until the pres- 

 sure becomes so great as to condense the air contained between the grains 

 sufficiently to produce the heat required for firing those grams, which are then 

 consumed more or less rapidly, as they are fine or coarse. We have, then, 

 first the burning hi succession of a small part of the charge ; then the im- 

 mensely rapid, though not instantaneous, kindling of every grain composing 

 it; and then the consumption of those grams, which is not accomplished 

 without time. It is a task for the conception to grasp these events, following 

 one another in distinct succession ; each having its beginning, middle, and end, 

 and all being comprised in the period of -^-jth of a second (gun 4 feet long, 

 formula t = ^ s ). When we have mastered the imagination of these, we may 

 go further and combine with them the connected and contemporaneous action 

 of the bah 1 , which passes from rest to motion, and through every gradation of 

 velocity up to 1,600 feet a second, and leaves the gun as our historical period 

 of o-^th of a second expires. 



The expansive force of gunpowder, which must be resisted by the strength 

 of the cannon, depends almost entirely upon the circumstances under which 

 it is fired. Count Rumford has shown, by his experiments made about sixty 

 years ago, that if the powder be placed hi a closed cavity, and the cavity be 

 two thirds filled, the force will exceed 10.000 atmospheres, or 150,000 pounds 

 upon the square inch ; and he estimates that if the cavity be entirely filled 

 with the grained powder, and restrained to those dimensions, the force will 

 rise to 50,000 atmospheres. My own experience, made in bursting wrought 



