150 Effects of Heat modified ly Compression. 



results of the best quality. I therefore procured at the 

 foundry a large mass of iron (/), intended, I believe, for 

 driving piles, and which, after allowing for the counterpoise 

 of the beam, gave a direct pressure of 8*1 cwt.; and I could, 

 at pleasure, diminish the compressing force, by placing a 

 bucket (e) at the extremity of the lever, into which I intro- 

 duced weights, whose effect on the ultimate great mass was 

 known by trial. Many barrels failed in these trials : at last 

 I obtained one of small bore, inch 0-54, which gave two 

 good results on the 22d of June 1804. 



No. 8. — Wishing to ascertain the least compressing force 

 by which the carbonate could be effectually constrained in 

 melting heats, I first observed every thing standing firm in 

 a heat of above 20°; I then gradually threw weights into the 

 bucket, till the compressing force was reduced to 2 cwt. 

 Till then, things continued steady ; but, on the pressure 

 being still further diminished, metal began to ooze out at 

 the muzzle with increasing rapidity. When the pressure 

 was reduced to l-i- cwt. air rushed out with a hissing noise. 

 I then stopped the experiment, by pouring water oh the 

 barrel. The piece of chalk had lost 12 per cent. It was 

 •white and soft on the outside, but firm and good in the 

 heart. 



No. 9. — An experiment was made with chalk, in a little 

 tube; to this, one grain of water was added. I had intended 

 to work with 4 cwt. only; but the barrel was no sooner 

 placed, than an exudation of metal began at the muzzle, 

 owing, doubtless, to the elasticity of the water. I imme- 

 diately increased the pressure to 8-1 cwt. by removing the 

 weight from the bucket ; when the exudation instantly 

 ceased. I continued the fire for three quarters of an hour, 

 during which time no exudation happened ; then all came 

 out remarkably clean, with scarcely any contamination .of 

 metal. The loss amounted to 2*58 per cent. The substance 

 was tolerably indurated, but had not acquired the character 

 of a complete stone. 



In these two last experiments, the bore being small, a 

 pyrometer could not be admitted. 



On the 5th of July 1804, I made three very satisfactory 



experiments 



