in the Pyrites, 107 



degree of fire. For, according as a copper-ore 

 happens to be burnt too little, or too much, the 

 magnet manifefls-a greater or lefs degree of brifk- 

 nefs on it : and mould I attempt the making a 

 proof or two only, it would be impoflible fo exact- 

 ly, in the other proofs, to hit again on the due 

 length of time, and the proper degree of fire : or, 

 mould I work feveral proofs at once, as, for that 

 end 1 have conftrudted my reverberating furnace 

 for defulphuration, one and the fame degree of 

 fire could not pofiibly be applied to each apart : 

 not to mention, that of many ores I have only 

 employed fmall parcels, being only provided with 

 fuch -, whence 'tis eafy to judge, a fmall parcel 

 may be fooner fitted for the magnet than a larger : 

 and laftly, 'tis probable, pyrites- copper- ores do, to- 

 gether with the two capital metallic earths, con- 

 tain alio a crude, unmetallic earth, and that in 

 various proportion, and which is neither to be 

 weighed nor mcafured. So that, befides the cop- 

 per, there is fomething clfe in the pyrites, that 

 hinders and weakens the effects of the magnet. 



But, (till more certainly to difcover the propor- 

 tion of copper the magnet can bear in the iron, I 

 melted both thefe metals together in different pro- 

 portions •, as for inftance, filed iron, and filed 

 copper, in various layers, committed to a crucible, 

 with a Mux confiding of two parts of the black flux, 

 and glafs, and one of borax and fait of tartar, to be- 

 tween one and f and two parts of metal, and found 

 the magnet could bear in the iron half the copper; 

 nay, 1 doubt not, a greater proportion, which I 

 cannot at prefent afcertain, as feveral proofs mif- 

 carried with me. Being engaged in thefe experi- 

 ments, I was willing to know what, and how 

 much of other metals the magnet could fuffer in 

 iron^ and the refult was as follows. 



(1.) Iron 



