SCHEELE, PRIESTLEY, AND CAVENDISH 139 



reaction - taking the gaseous bodies fully into account - 

 ignoring the weight of heat produced or disappearing, and 

 leaving a special fire-stuff (phlogiston) out of consideration. 

 This was first carried out by Lavoisier, who lived from 1743 

 to 1794 in Paris .^ 



The new discoveries showed that everything was much 

 simpler than people had previously dared to think, and it 

 further continued to appear that in the case of all different 

 kinds of substances, of which new varieties were continually 

 being discovered and in all their changes, combinations, and 

 separations, we only have to deal with matter of invariable 

 weight, which simply arranges itself in various ways. Heat, 

 and light, which for Scheele were still objects for investiga- 

 tion on the same footing as the gases with which he was con- 

 cerned, thus fell outside the limits of the problem; chemistry 

 became purely the science of the internal composition of the 



^ Lavoisier also lays the main stress upon the facts, only that he allows 

 it to appear as if they had all been discovered by himself, whereas in very 

 many cases he is only giving reports or variations of what had become 

 known to him in other ways from his contemporaries, especially from 

 Black, Priestley, Cavendish, and Scheele, or from what had already been 

 published. A particular mistake often met with is that of imagining the 

 first use of the balance in chemical investigation to go back to Lavoisier, 

 For not only had Black carried out important and illuminating investi- 

 gations by means of the balance, but even Boyle, and others before him, 

 had already followed the changes in weight taking place in chemical 

 transformations, for instance, the increase in weight when metals are 

 calcined (oxidised). It is obvious that the use of the balance greatly 

 increased as soon as the invariability of the weights of the substances 

 taking part in chemical change had been rendered probable; and that 

 after the discoveries of Scheele and Cavendish had taught us the compo- 

 sition of air and water, and also of nitric acid, the investigation of other 

 substances, such as carbonic acid, sulphuric acid, was soon carried out 

 successfully; this was done by Lavoisier, but he did not state correctly 

 the origin of these discoveries. For details of all this the reader is referred 

 to Kopp's History of Chemistry (Brunswick, 1843), vol. i, pages 302-312, 

 vol. 3, pages 204-206, 266-271. Kopp, who had a thorough knowledge 

 of history, remarked in the latter place quite rightly: ' . . . but the object 

 of history is not to make laudatory speeches, and not its smallest, and for 

 our time, least useful, task, is to show how every appropriation of the 

 achievements of others later becomes revealed, and produces precisely the 

 opposite effect in the case of those who hope thereby to increase their 

 own reputation.' Compare previous note concerning Lavoisier and 

 Black, p. 128. 



