﻿ON CONSTRUCTING CANNON OF GREAT CALIBER. 3 



Society. If it be instantaneous, then it must be evident that no other substance can 

 be fired with a greater rapidity. For instantaneousness, bearing the same relation to 

 time that a point does to space, can admit of no degrees. Both are existences 

 without extension, and we cannot say of any tAvo events that one is more instan- 

 taneous 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 kno-mi, 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 in 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 thmgs during that whole course. 



First, Count Eumford has proved that the burning of the grains is slow, or that a 

 sensible time is required with each grain 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 com- 

 municating the fire to the centre rather than to one end of the charge, which ought 

 evidently to take place if the fire is communicated from one grain to another in suc- 

 cession, as this communication, being in both directions, when proceeding from the 

 middle, would requii'e but half the time that is required when proceeding from one 

 end, and ought to produce a sensible increase in the velocity of the shot. I think, 

 therefore, that these two facts warrant the followmg mference as to the course of 

 the action durmg the production of the force. When the fire I'caches the charge 

 from the touchhole, the nearest grains become kindled ; the hot fluid evolved is 

 thrown farther into the charge, and the burning succeeds successively until the 

 pressure becomes so great as to condense the au- contained between the grains suffi- 

 ciently to produce the heat required for firing those grains, which are then consumed 

 more or less rapidly, as they are fine or coarse. We have, then, first the burnmg in 

 succession of a small part of the charge ; then the immensely rapid, though not 

 instantaneous, kindling of every grain composing it; and then the consumption of 

 those grains, which is not accomplished without time. It is a task for the con- 

 ception to grasp these events, following one another in distinct succession ; each 

 hanng its beginning, middle, and end, and all being comprised in the period of 

 a^th of a second (gun 4 feet long, formula t ^ -}. When we have mastered the 

 imagination of these, we may go further and combine with them the connected and 



