CG ©N THE DOCTRINE OF PHLOGISTON* 



alledges of ihis kind is of any confequence to the main argu- 

 ment. On the other hand, he fays, p. 42, with an air of 

 triumph, but before the victory, that " having additional dif- 

 ficulties to ftruggle with, I have been under the neceflity of 

 adopting new, and fometimes contradictory, opinions, in my 

 explanations and defences." 

 The difcuffion Now I really am not fenfible of any difficulty whatever in 

 m difficulty. * n ' s difcuffion; and in advancing this he feems not to have 

 apprehended my fentiments with refpect to the calces of me- 

 tals. If he was acquainted with my publications, he would 

 have found that there was nothing either new, or contradic- 

 tory, in what I have now advanced on this fubject, or that of 

 the compofition of charcoal ; though that I have fometimes 

 changed my opinions on philofophical as well as other fub- 

 jecls, I readily acknowledge, and without any feeling of 

 fhame. 

 Finery cinder In my opinion, and that of long Handing, the black calx of 

 contains water ; rorij commonly called finery cinder, contains no oxigen, but 

 ©n adding phlo- on ty water ; and though the calx of zinc, and the yellow calx 

 gifton) water of lead, called mqficot, do contain fome, it is fo little that I 

 wIyi$feparated. cannot ^^ ^ Mr Cruickfliank fayg< p ^ that << if 



water be the only fubfiance contained in oxides, heat alone 

 ought at leaft to revive fome of them, and that in this cafe 

 nothing but water would be feparated." Now what I main- 

 tain is, that when finery cinder is revived, (which, however, 

 is not done without the introduction of phlogiflon) nothing but 

 water is feparated from it. 

 The prefent let. Oxigen is undoubtedly contained in the red calx of lead,. 



to r that C obta. d called minium > and m that of mercury ; but I fay that even 

 thefe cannot be revived without the introduction of phlogiflon. 

 This fubjed, however, I wave for the prefent, wifliing to 

 difpatch that of the air from finery cinder and charcoal before 

 we proceed to any other j and I wifli Mr. C. to attend to the 

 following obfervations, which I mall now ftate more difTinclly 

 than I have done before, that it may be the eafier for our rea- 

 ders to judge between us. 

 Mr. C*s theory I« Mr. Cruickfhank's hypothec's requires that, in the pro- 

 demands that cefs of heating finery cinder and charcoal, the oxigen in the 

 quitlron to form finery cinder mould quit that fubftance, and unite with carbon 

 fixed air with i n the charcoal, in order to form fixed air. Since, however, 



then^returntt) tn * s ^ xed a * r * s lo ^ e decompofed by iron, the oxigen which it 

 tke iron in order 4 has 



