On the Nature of the Earths. 63 



itig the decomposition of either barytes, magnesia, or lime ; 

 nor can I sgree with your correspondent O., that the ob- 

 jections of Klaproth and Tihawski, to the accuracy of the 

 results of Toudi and Ruprecht's experiments, do not affect 

 the purpose for which he has introduced them. These re- 

 sults, Mr. O. tells" us, were noticed by Mr. Robert Kerr, in 

 the second English edition of Lavoisier's Elements of Che- 

 mistry, accompanied with some original remarks, which 

 O. copies. I am as .much inclined to allow Mr. Kerr all the 

 merit he deserves, as his friend Mr. O. can be, and am 

 ready to acknowledge that his remarks are striking, parti- 

 cularly the following, mentioned in the note, that " from 

 analogy we may presume potash to be a metallic substance 

 in some hitherto unknown state of combination." But, sir, 

 this conclusion was drawn from incorrect data, viz. from 

 some experiments published in the Transactions of the Turin 

 Academy, (from which O. says Mr. Kerr's opinions re- 

 ceived corroboration !) which gave reason for supposing 

 soda to be a modification of magnesia. Now we know 

 that soda is not a modification of magnesia, neither had 

 magnesia, at that time, been proved to be a metallic oxide, 

 for Toudi and Ruprecht's experiments were far from satis- 

 factory. I cannot therefore allow Mr. Kerr any other merit 

 on this head, than that of having made a very fortunate 

 guess at this philosophical senigma; for the mere supposition 

 of a fact, and the proof, are very different things. Ages 

 ago the alchemists supposed gold to be a compound body, 

 and all the world knows how earnestly and how fruitlessly 

 they laboured to prove it so. Fire may be a compound, 

 and there is just reason to think it is ; but what is all this 

 but conjecture? — a field of all others the easiest to indulge 

 in; and if men are continually guessing, it would be indeed 

 extraordinary if they did not sometimes approach the truth. 

 But indeed O., a few lines further-, seems to be perfectly 

 of my opinion, allowing at the time Mr. Kerr made his 

 conjectures they might have appeared chimerical ; that is, 

 allowing they were neither more nor less than so many 

 guesses. But, I repeat, I am far from wishing; to deprive 

 Mr. Kerr of any well-earned praises, (and his Translation 



of 



