i|fi2 ComhiiJIhii of GiiiipiiwJfr in a Clofed Veffel. 



in a vertical ftjme, and could be raifod and lowered in tlic intervals between the experi- 

 ments by a ftrong le\'er. 



The end of the barrel \ras covered with gold, in order to prevent as much as poffible its 

 being corroded by the elaftic vapour, which, when the weight is not heavy enough to con- 

 fine it, cfcapes between the end of the barrel and the flat furface of the hemifphere ; but 

 even this precaution was not found to be fufficient to defend the apparatus from injury. 

 The (harp edge of the barrel, at the mouth of the bore, was worn away almoft imme- 

 diately ; and the flat furface of the hemifphcre, notwithftanding it was of hardened 

 ftcel, and very highly polifl>ed, was fenfibly coiToded. Tlie corrofion of the mouth of the 

 bore, by which the dimenfions of the furface, upon which the generated elaflic fluid a£led, 

 were rendered very uncertain, would alone have been fufficient to have rendered all the 

 Count's attempts to determine the force of fired gun-powder abortive, had he not found 

 means to remedy the evil. The method he purfued for this purpofe was as follows: Hav- 

 ing provided fome pieces of very good, compadt fole-leather, he caufed them to be bcatert 

 upon an anvil with a heavy hammer, to render them llill more compacl ; and then, by 

 means of a machine made for that purpofe, cylindrical floppers of the fame diameter prc- 

 cifely as the bore of the barrel, and 0,13 of an inch in length, (that is to fay, the thick- 

 iiefs of the leather) were formed of it ; and one of thefe floppers, which had previoully been 

 gieafcd with tallow, being put into the mouth of the piece after the powder had been in- 

 troduced, and being forced into the bore till its upper end coincided with the end of die 

 barrel, upon the explofion taking place, this ftopper (being prefled on the one fide by the 

 generated elaftic fluid, and on the other by the hemifphere loaded with the whole weight 

 employed to confine the powder) fo completely clofed the bore, that when the force of the 

 powder was not fufficient to raife the weight to fuch a height that the ftopper was adually 

 blown out of the piece, not a particle of the elaftic fluid could make its efcape. And in 

 fhofe cafes in which the weight was aftually raifed, and the generated elaftic fluid made its 

 cfcapc, as it did not corrode the barrel in any other part but juft at the very extremity of the 

 tore ; the experiment by which the weight was afcertalned, which was juft able to counter- 

 balance the preflure of the generated elaftic fluid, was in no wife vitiated either by the in- 

 creafed diameter of the bore at its extremity, or by any corrofion of the hemifphere itfelf -, 

 for as long as the bore retained its form and its dimenfions in that part to which the efforts 

 of the elaftic fluid were confined, that is, in that part of the bore immediately In contaft with 

 the Icrwer part of the ftopper, the experiment could not be affefted by any imperfe^lion of 

 the bore either above or below. 



- The powder made ufc of in thefe experiments was of the beft quality, being that kind 

 Called /w/i/r^ (/<• cA/j/^ by the French, and very fine grained, and it was all taken from the 

 •fame^iarcel. Care was taken to dry it very ti«roughly, and the air of the room in which it 

 was weighed out for ufe was very dry. The weights e-nployed for weighing the powder 

 were German apothecary grains, 104,8 of which make too grains troy. 1 lie weights em- 

 ployed 10 confine thr elaftic vapour generated in the combuftion of the pow<!er, are reduced 

 from Bavarian pound, , in which they were originally exprefled, to pounds avoirdupois. The 

 meafurcs of length were all taken in Englifli feet and inches. The e>:periments were all 

 made ifi the open air, ia the court-yard of the arfciial at Munich, and they were all made in 



fair 



