Effects of Htat modified lij Compression. 14Q 



tlie barrel by means of a plug fixed by solder only ; which 

 method had this peculiar advantage^ that I could shut and 

 open the barrel without having recourse to a workman. In 

 these trials, though many barrels yielded to the expansive 

 force, others resisted it, and afforded some results that were 

 in the highest degree encouraging, and even satisfactory, 

 could they hav'ebeen obtained with certainty on repetition 

 of the process. In many of them chalk, or common lime- 

 stone previously pulverised, was agglutinated into a steny 

 mass, which required a ^mart blow of a hammer to break it, 

 and felt under the knife like a common limestone ; at the 

 same time the substance, when thrown into nitric acid, dis- 

 solved entirely with violent effervescence. 



In one of these experiments, owing to the action of heat 

 on the cartridge of paper, the baked clay, which had been 

 used to fill the barrel, was stained black throughout, to the 

 distance of two-thirds of the length of the barrel from its 

 breech. This circumstance is of importance, by showing, 

 that though all is tight at the muzzle, a protrusion may take 

 place along the barrel, greatly to the detriment of complete 

 compression : and, at the same time, it illustrates what 

 has happened occasionally in nature, where the bituminous 

 matter seems to have been driven by superior local heat from 

 one part of a coaly bed, though retained in others, under the 

 game compression 5 the bitumen so driven off being found, 

 in other cases, to pervade and tinge beds of slate and of 

 sandstone. 



I was employed in this pursuit in spring 1800, when an 

 event of importance interrupted my experiments for about a 

 year. But I resumed them in March 1801, with many new 



by which part of the barrel was spread out to a flat plate, and the furnace 

 was blown to pieces. Dr. Kennedy, who happened to be present on this 

 occasion, observed, that notwithstanding this accident, the time might come 

 when we should employ water in tliese experiments to assist the force of 

 compression. I have since made great use of this valuable suggestion: but he 

 scarcely lived, alas! to see its applifition ; for my first success in this way 

 took place during his last illness. — 1 have been exposed to no risk in any other 

 experiment with iron barrels; matters being so arranged that the strain 

 against them has only commenced in a red heat, in which the metal has been 

 io far %often?d as to yield by laceration like a piece of leather. 



K 3 plans 



