29" Effects of I leaf modified ly Compression, 



showed a saline fracture, composed of innumerable facettes. 

 The carbonate adhered, from end to end, to the lube, and 

 incorporated with it, so as to render it impossible \o ascer- 

 tain what loss had been sustained. In general, th. line of 

 contact was of a brown colour; yet there wai; no room for 

 suspecting the presence of any foreign matter, except, per- 

 haps, from the iron rod which was used in ramming down 

 the chalk. But, in subsequent experiments, T have observed 

 the same brown or black colour at the union of the carbo- 

 nate with the porcelain tubes, where the powder had been* 

 purposely rammed with a piece of wood ; so that this co- 

 lour, which has occurred in almost every similar case, re- 

 mains to be accounted for. The carbonate effervesced vio- 

 lently with acid ; the substance in contact with the tube 

 doing so, however, more feebly than in the heart, leaving a 

 copious deposit of white sandy matter, which is doubtless a 

 part of the tube, taken up by the carbonate in fusion. 



On the 24th of March I made a similar experiment in a 

 stout gun-barrel, and took some care, after the application 

 of heat, to cool the barrel slowlv, with a view to crystalliza- 

 tion. The whole mass was found in a fine state, and un- 

 touched by (he lead ; having a seftii-transparent and saline 

 structure, with various facettes. In one part I found the 

 most decided crystallization I had obtained, though of a 

 small size : owing to its transparenov it was not easily vi- 

 sible till the light was made to reflect from the crystalline 

 surface, which then produced a dazzle, very observable by 

 the naked eye : when examined by means of a lens, it was 

 sepn to be composed of several plates, broken irregularlv in 

 the fracture of the specimen, ail of which are parallel to each 

 other, and reflect under the same anajle, so r.s to unite in 

 producing the dazzle. This structure was observaDle equally 

 well in both parts of the broken specimen. In a former ex- 

 periment, as large a facctle was obtained in a piece of solid 

 chalk; but this result was of more consequence, as having 

 been produced from chalk previously pounded. 



The foregoing experiments proved the superior efficacy of 

 iron vessels over those of porcelain, even where the thickness 

 v'as not great; and I persevered in making a great many 



experiments 



