183 CULMINATING MERCURY. 



leaf tin ; the bulb of a Fahrenheit's thermometer was made just to 

 touch the surface of the oil, which was then gradually heated till 

 the powder exploded, as the mercury reached the 368th degr. 



" Desirous of comparing the strength of the mercurial compound 

 with that of gunpowder, I made the following e.\p liment in the 

 presence of my friend Mr. Abernethy. 



tf Finding that the powder could not be fired with flint and 

 steel, without a disagreeable noise, a common gunpowder proof, 

 capable of containing eleven grains of fine gunpowder, was filled 

 with it, and fired in the usual way : the report was sharp, but not 

 loud. The person who held the instrument in his hand felt no re. 

 coil j but the explosion laid open the upper part of the barrel, 

 nearly from the touch-hole to the muzzle, and struck off the hand 

 of the register, the surface of which was evenly indented, to the 

 depth of 0.1 of an inch, as if it had received the impression of a 

 punch. 



" The instrument used in this experiment being familiarly known, 

 it is therefore scarcely necessary to describe if. : sullkt. it to say, 

 that it was brass, mounted with a spring registrr, the 

 hand of whL.h closed up the muzzle, to receiv and IT' ' 



nee of the explosion. The barrel w.s 

 and nearly half an inch thick, except where .. 

 impaired half its thickness. 



" A gun belonging to Mr. Keir, an ingenious artist of i. am 

 Town, was next charged with seventeen grains of the mercurial 

 powder, and a leaden bullet. A block of wood was placed at 

 about eight yards from the muzzle to receive the ball, and the gun 

 was fired by a fuse. No recoil seemed to have taken place, as the 

 barrel was not moved from its position, although it was in no * 

 confined. The report was feeble; the bullet, Mr. Keir conceived, 

 from the impression made upon the wood, had been projected with 

 about half the force it would have been by an ordinary charge, 

 or sixty-eight grains, of the best gunpowder. We therefore re- 

 charged the gun with thirty. four grains of the mercurial powder; 

 and as the great strength of the piece removed any apprehension of 

 danger, Mr. Keir fired it from his shoulder, aiming at the same 

 block of wood. The report was like the first, sharp, but not 

 louder than might have been expected from a charge of gunpowder. 

 Fortunately Mr. Keir was not hurt; but the gun was burst in an 

 extraordinary manner. The breech was what is called a patent 



