Effects of Heat modified ly Compression. 145 



of 30 lbs. producing a pressure of 90 lbs. ; but I found this 

 not sufficient. I than hung on a weight of 1 cwt., or 

 112 lbs.; by which a compressing force was applied of 

 3 cwt., or 336 lbs. Very little metal was seen to escape, 

 and no sound of ebullition was heard. The chalk in the 

 body of the large tube was reduced to quicklime ; but what 

 lay in the inner tube was pretty firm, and effervesced to the 

 last. One or two facettes, of good appearance, were like- 

 wise found. The contents of the small tube had lost but 

 2*6 per cent.; but there was a small visible intrusion of 

 metal, and the result, by its appearance, indicated a greater 

 loss. I considered this, however, as one point gained ; that 

 being the first tolerable compression accomplished by a de- 

 terminate force. The pyrometer indicated 22°. 



This experiment was repeated the same day, when a still 

 smaller quantity of metal escaped at the muzzle; but the 

 barrel had given way below, in the manner of those that 

 have yielded for want of sufficient air. Even this result was 

 satisfactory, by showing that a mechanical power, capable 

 of forcing some of the barrels, could now be commanded. 

 The carbonate in the little tube had lost 20 per cent.; but 

 part of it was in a hard and firm state, effervescing to the 

 last. 



No. 2. — On the 21st of June I made an experiment with 

 another barrel, with the same circumstances. I had left an 

 empty space in the large tube, and had intended to introduce 

 its muzzle downwards, meaning that space to answer as an 

 air-tube ; but it was inverted by mistake, and the tube, en- 

 tering with its muzzle upwards, the empty space had of 

 course filled with metal, and thus the experiment was made 

 without any included air. There was no pyrometer used ; 

 but the heat was guessed to be about 23° where the subject 

 of experiment lay. The barrel, when opened, was found 

 full of metal, and the cradle being laid flat on the table, a 

 considerable quantity of metal ran from it, which had un- 

 doubtedly been lodged in the vacuity of the large tube. 

 When cold, I found that vacuity still empty, with a plating 

 of metal. The tube was very clean to appearance, and, 

 when shaken, its contents were heard to rattle. Above the 



Vol. 25. No. QS.Juhj 180G. K little 



