153 . Experiments on various Earths. 



My first experiments were made with pure earths, clay, 

 silex, lime, barytes, and strontian, considering them as 

 metallic oxides, whose oxygen might be carried off by pre- 

 senting them with carbon at a high temperature, and secured 

 from the access of air. This reasoning I carried into prac- 

 tice by cementation for hours, and sometimes for three or 

 four days. Various earths were exposed imbedded in finely- 

 pounded charcoal. These were afterwards freed from the 

 carbonaceous matter, and exposed to fusion in high heats 

 in a wind furnace. Clay and silex I found infusible under 

 the highest heat that could be urged. Barytes, lime, and 

 strontian, were fused with various proportions of charcoal, 

 but no result occurred from which any conclusion could be 

 drawn favourable to the idea of either a part, or the whole, 

 of the oxvgen having been removed from the respective 

 earths, nor was it found that any loss of weight took place, 

 (as is the case with iron ores,) which would not have oc- 

 curred by simply exposing these substances to the same 

 temperature. The glasses resulting from the different fu- 

 sions were various in colour, whitish, opaque, brownish, 

 and black. The only circumstance which indicated change 

 was in the barytes, the different fusions of which always 

 gave a thin pellicle on the surface that never was resolved to 

 glass, but was alwavs strongly alkaline. This, at the time, 

 I could not account for, nor tii! Mr. Davy's discoveries were 

 announced. The probability then appeared, that this was a 

 portion of the barvtium, which, during the operation, had 

 been metaibzed, but, in cooling, had again attracted oxygen 

 from the atmospheric air, and had passed into the state of 

 an alkaline earth. 



After many experiments, I at that time abandoned the 

 pursuit, and arranged those specimens of glass which ap- 

 peared most fit lor future examination, should the subject 

 present itself under any new shape. Some years afterwards 

 having occasion otherwise to examine the boxes in which 

 these .specimens were kept, I was much surprised to find, 

 that nianv of the glasses had become converted into a fui<; 

 powder, [was induced, from a similar circumstance hav- 

 ing liken place with a gUfig of manganese, to infer* that in 



the 



