420 



TRANSACTIONS OF THE AMERICAN INSTITUTE. 



this is another cause of the retardation to its motion outward. Although 

 for ninety-nine hundredths of the whole time the heat is radiating from the 

 surface of the bore, the velocit}' with which it leaves is much less than the 

 velocity with which it is received, because the difference iu the tempera- 

 ture of the gun and the atmosphere occupying the bore is much less 

 than the difference of temperature between the metal of the gun and the 



Ji^f3, 



gases ejecting the shot by their pressure. The atmos- 

 phei'e occupying the bore receives the heat by radiation, 

 in the intervals between firing quickly from the imme- 

 diate surface, and less quickly a little distance beyond; 

 and so again the heat flows from the metal of the gun 

 with reduced velocity as the distance increases from 

 the bore, leaving the point of highest temperature in 

 the mass of metal, but not far from the surface of the 

 bore. {See Fig. 13.) Its effect toward causing 

 rupture may be illustrated by taking a cylinder 

 »f pine wood a few inches in length and a cross- 

 section like the diagram, and providing a wedge 

 similar in form to a bayonet, but truly tapered to 

 a point from a cross-section at the head, the same 

 as the lines representing the place and quantity 

 of heat on the diagram, showing its effects by. inter- 

 mittent communication of heat. {Fig. 13.) If the 

 point of this wedge be set upon the end of the 

 wooden cylinder at the point supposed to be the 

 point of greatest heat, according to the theory 

 above, and by a blow driven into the end- wood, it 

 will penetrate so as to make an impression like the 

 inner line of the diagram. A second blow, driving 

 it further into the wood, penetrating as if to the 

 second line of the diagram, and expanding the wood, 

 will cause a fracture inward toward the surface of 

 the bore, first; a third or fourth blow will split it to 

 the outside. And thus guns burst, the first frac- 

 ture occurring on the inside, and afterward opening to the outer surface. 



Mr. Edward Cooper was of opinion that guns generally burst through 

 the vent. 



The question was continued to the next meeting, and that of " Inland 

 Navigation " was selected for the 9th of January. 

 ' Adjourned. Thomas D. Stetson. Secretary. 



•■} 



American Institute Polytechnic Association, 

 December 18, 1862. 

 The Chairman, S. D. Tillman, Esq., presiding. 



Mr, Stetson, the Secretary, exhibited to the meeting specimens of the 

 fiber of Sisal hemp, also some of the raw material, green leaves of the cac- 

 tus species — the Axgave Americana, several feet iu length. This material 



