160 Experiments on various Earths. 



III. — 100 grai i carbonate of barytes in a similar ex- 

 periment ' 'at« . only 41 \ grains of iron *, 



IV. — 100 grains of carbonate of strontian deprived of its 

 carbonic acid oxidated 21 j grains of iron. 



V. — 100 grains Q,f,potash oxidated 28 grains of iron. 



VI.— 100 grains of salt of tartar oxidated 22 grains of 

 iron. 



VII. — 100 grains of calcined borax oxidated 3} grains of 

 iron, i 



VIII. — 100 grains of window glass, composed of two parts 

 of soda and two of Lynn-sand, oxidated 4^ grains. 



IX. — 100 grains of bottle glass oxidated 3 grains of iron. 



X, — lOOgrains of roasted ironstone, containing iron 48*5 '> 

 oxygen 15-5; earths 36* — 100, oxidated 33 grains. 



XI. — 100 grains of manganese in a similar experiment 

 oxidated 25 1 grains. 



It appeared from these experiments, that either barytes 

 contained the greatest dose of the oxidable principle, or that 

 it gave it out to iron with the greatest facility. It was there- 

 fore fixed upon as the most proper subject for further expe- 

 riment, the details of which I shall state as shortly as pos- 

 sible. 



XII.--^100 grains of pure barytes were exposed to a heat 

 of 168° jrf Wedgwood. An emerald-coloured glass was 

 obtained, which, in cooling, arranged itself into numerous 

 small squares; the surface was covered with a crust or pel- 

 licle very like an oxide of nickel. 



XIII. — 100 grains of barytes mixed with 10 grains of 

 charcoal were exposed to the same heat. The result was a 

 dark- green glass, accompanied with a similar saline crust, 

 rather more of a coppery colour. The charcoal had disap- 

 peared . 



XIV. — The same experiment was repeated with 20 grains 

 of charcoal. The fusion, though exposed to as high a heat, 

 was less perfect. A greater quantity of the apparent oxide 

 V*as formed, and a proportionably less quantity of glass. 



* The result of this experiment being the same as Experiment II., Mr. M. 

 has probablv made a mistake in copying his notes. — Edit. 



2 XV.— This 



