EjVimaU of the Force employed in burjlitig an Iron Baryel. ^Sj 



rot only completely burft afunder, but the two halves of it were thrown upon the ground in 

 different dire£lions ; one of them fell clofe by the Count's feet, as he was ftanding near the 

 machinery to obferve more accurately the refult of the experiment. 



From fonie former experiments with fmall iron wire. Count Rumford deduces, that a cy- 

 linder of that metal, whofe tranfverfe fedion is one inch, would be able to fuftain 63466 

 pounds without being broken. But for greater accuracy, he caufed feveral fmall pieces to be 

 cut out of the folid half of the barrel which was broken. From four experiments with 

 pieces whofe diameters w6re refpedlively in thoufandth parts of an inch, fifty, fixty, fixty- 

 Cix and feventy-Gx parts, which were broken by a direft pull, it was found that the medium 

 weight required to break one inch of this iron was in pounds avoirdupois 63173. The varia- 

 tions in the refult were fuch as to render the fecond figure (expreffing thoufands) uncer- 

 tain. Our author computes the reGflance of the barrel from the area of the furface of frac- 

 ture, namely, 6i inches, by ufing this as a fimple multiplier, which gives 410624-?- pounds. 

 And this force being confidered as applied to a furface of half an inch, which is the area of 

 a longitudinal feftion of the bore of the barrel, and reduced into atmofpherts, by allowing 

 15 pounds avoirdupois for the medium preffure of the air upon a fquare inch, gives 54750 

 atmofpheres for the meafure of the force exerted for overcoming fuch a refiftance. This 

 force, enormous as it may appear, is fuppofed by the Count to be Ihort of the real initial 

 force of the elaftic fluid generated in the combuftion of gunpowder, becaufe he thinks it 

 probable that the barrel was in fad burft before the generated elaftic fluid had exerted all 

 its force. On this head of probabilities I would venture to make a remark, that the iron in 

 the barrel may perhaps be confidered as not exadly in the fituation of the pieces which our 

 author broke in his engine by a direft pull. For in thefe laft it may reafonably be fuppofed, 

 that the whole preffure of cohefion was equally aded on till the moment of frafture ; 

 ■whereas in the barrel the frafture may, from the fpring of the metal and other circum- 

 ftances, be fuppofed to have proceeded from the inner to the outer furface by a progreflion 

 or tearing afunder, which, however fwift, muft have rendered the divifion more eafy. But 

 at all events, whatever may be the force of this remark, it can in no refpcG invalidate fuch 

 eonclufions as were drawn ffom the adual lifting of great weights by raifing the hemifpheri- 

 cal cover of the barrel. 



A fet of experiments were inftituted with an apparatus of the kind here defcribed, for the 

 purpofe firft of determining the expanfive force of the elaftic vapour generated in the com- 

 buftion of gunpowder in its various ftates of condenfation, and the ratio of its el.ifticity to its 

 denfity ; and fecondly, of peafuring by one decifive experiment the utmoft force of this fluid 

 in its moft denfe ftate ; that is to fay, when the powder completely fills the fpace in which 

 it is fired, and in which the generated fluid is confined. A numerous feries of experiments 

 arc tabulated in the Count's IMemoir. 



The dimenfions of the barrel made ufe of in thofe experiments were as follow :' 



Diameter of the bore at its muzzle = 0,25 of an inch. 



Joint capacities of the bore and of its vent-tube cxclufivc of the fpace occupied by the 

 leathern (topper = 0,08974 of a cubic inch. 



Quantity of powder contained by the barrel and its vent-tube when both were quite full, 

 exclufiveof the fpace occupied by the leathern ftopper, 25,641 German npotliccaries grains, 

 = 24 1 grains troy, 



3 O 2 The 



