- From STRONTIJN. 31 



*' confifls of about half its weight of water." From thefe ob- 

 fervations DrPRiFSTLEY inferS; that water enters into the com- 

 pofition of fixed air, nay, that it is this ingredient which is 

 eflential to the aeriform condition of the acid. He extends the 

 idea to all aerial fluids, and hence draws a futile argument 

 againft Mr Cavendish's glorious difcovery of the compofition 

 of water. 



3. It is unnecefTary to tranfcribe the words of Mr Watt 

 junior, who fpeaks on the authority of Mr [osfah Wedgewood 

 junior^ to nearly the fame purpofe or thofe of M. Sage, FouR'^ 



CROY and Pelletier. who ftrangely aflert, that this fubilance 

 is abfolutely unchangeable by heat. 



4. From this general opinion, however, I am obliged to dif- 

 fent, having found, that the fixed air can be expelled from the 

 native aerated barytes by heat alone, if fufficiently intenfe ; a 

 circumftance that mufh prove fatal to the theory founded on its 

 iuppofed impra(5ticability. The heat which anfwers this pur- 

 pofe is that of a fmith's forge, when the fire is fldlfully ma- 

 naged. By its afliftance, I have oftentimes deprived the bary- 

 tic fpar of its acid either entirely or nearly fo. 



5. I NEED not detail the particulars of more than of one expe- 

 riment. In feveral trials, however, it may not be improper to 

 remark, I was difappointed, in confequence of the barytes, vehe- 

 mently heated, adling as a flux on the clay of the crucible, cor- 

 roding holes in it and making its efcape, leaving as its only ve- 

 ftige a green-coloured vitreous glazing on the infide of the cru- 

 cible. At firfl: I employed crucibles made of pure Stourbridge 

 clay, bvit was, from the circumftance this moment mentioned, 

 obliged to have recourfe to thofe compofed of black lead, which 

 are able to refift and confine the heated fpar ; yet fometimes I 

 fucceeded even with thole of clay. 



6. A SOLID and pure mafs of the fpar, weighing 338.4 

 grains, was put into a black lead crucible, having a lid of the 



E 2 fame 



