Experiments on various Earths. 163 / 



XIX. — 115 grains of this carbonate were exposed for two 

 hours to a high red heat, and came out unchanged, both as 

 to weight and appearance. 



XX. — 40 grains pounded small were exposed to a high 

 white heat in a Cornwall clay crucible. A rough whitish 

 mass was obtained, which evidently had been fused — weight 

 36 grains. Loss 4 grains, supposed to be carbonic acid. 

 It was remarkable that the present result in cooling under- 

 went several shades of colour chiefly metallic ; a green suc- 

 ceeded by a vivid purple was the most decided. 



XX 1.-^-90 grains of this same carbonate, pounded small, 

 and 45 grains of iron filings were mixed together and fused: 

 the upper surface of the result was covered with a brownish 

 silvcrv enamel regularly, crystallized in small stars, each radi- 

 ating from a common centre. The thickness of this me- 

 tallic crust was nearly one-sixteenth of an inch. Its frac- 

 ture presented brilliant crystallized facets of a highly metal- 

 lic appearance. Under the barytium was found a jet black 

 shining glass, in which was inserted a smooth button of iron 

 weighing 20 grains. Beneath this button was another layer 

 of barytium regularly crystallized, but of a less metallic ap- 

 pearance than the upper stratum. In this experiment 90 

 grains of carbonate of barytes had furnished the means of 

 oxidating 25 grains of iron. 



XXII.-^O grains of carbonate of barytes, and an equal 

 quantity of iron filings, gave by fusion a double stratum of 

 barytium. Interposed between was a layer of black glass; 

 the crystallization and brilliancy of the upper stratum and 

 the general appearance of the whole were very similar to the 

 last experiment. The button of iron found in this result 

 weighed 33 grains. Loss 17 grains oxidated by 50 grains 

 of carbonate of barytes. 



This experiment was repeated with various proportions of 

 the carbonate of barytes and the iron, and with greater 

 quantities of matter, yet none of them were so perfect as 

 those detailed in the foregoing experiments. Greater quan- 

 tities of the apparent regulus were obtained, all tending to 

 the same crystalline arrangement, but inferior in point of 

 colour and brilliancy. 



L 2 I next 



