Effects of Heat modified hy Comptessio?}. -^gg 



saline grains, and scarcely effervesced in acid. It was pro- 

 bably quicklinic, formed by internal calcination, but in a 

 state that has not occurred in any other e.xperinient. 



The workman whom I employed to take out the remains 

 of the cradle, li;ul cut off a piece from the breech of the bar- 

 rel, three or four inches in length. As I was examining the 

 crack which was seen in this piece, I was surprised to see 

 the inside of the barrel lined with a set of transparent and 

 well defined crystals, of small size, yet visible by the naked 

 eye. They lay together in some places, so as to cover the 

 surface of the iron with a transparent coat ; in others they 

 were detached, and scattered over the surface. Unfortu- 

 nately, the quantity of this substance was too small to admit 

 of much chemical examination ; but I immediately ascer- 

 tained that it did not in the least effervesce in acid, nor did 

 it seem to dissolve in it. The crystals were in general trans- 

 parent and colourless, though a few of them were tincrcd 

 seemingly with iron. Their form was very well defined, 

 being flat, with oblique angles, and bearing a strong resem- 

 blance to the crystals of the lamcllated stvlbite of Haiiv. 

 Though niade above two years ago, thev still retain their 

 form and transparency unchanged. Whatever this sub- 

 stance may be, its appearance, in this experiment, is in the 

 highest degree interesting, as it seems to afford an example 

 of the mode in which Dr. Ilutton supposes n)an)' internal 

 cavities to have been lined, by the sublimation of sub- 

 stances in a state of vapour, or held in solution bv matters 

 in a gaseous form. For, as the crystals adhered to a part of 

 the barrel, which must have been occuj)icd by air during the 

 action of heat, it seems next to certain that tliey were pro- 

 duced by sublimation. 



The very powerful effects produced bv this last barrel, r!ie 

 size of which (reduced, indeed, by repeated oxidation) was 

 not above an inch square, made me very anxious to obtain 

 barrels of the same substance, which, beingj made of greater 

 size, ought to afford results of extreme interest, f ibiaid, 

 upon inquiry, that this barrel was not made of Svvedi.-li iron, 

 as I at first supposed, but of what is Knpwn by the name of 

 qI(I iub/c, from the figure of a sable stamped upon the batji; 



that 



