THE REVIVED THEORY OF PHLOGISTON. 563 



combustion unconscious of the fact and meaning of the relationship in 

 weight subsisting between the consuming and the consumed body, 

 but they were altogether ignorant of the j^art played by the air in the 

 phenomena which they so boldly and successfully attempted to ex- 

 plain. Torricelli's invention of the barometer, and Guericke's inven- 

 tion of the air-pump, were both, indeed, made during Beccher's early 

 boyhood; but years had to elapse before the consequent idea of- the 

 materiality of air could be domiciled, as it were, in human understand- 

 ings. And not until more than a century after Torricelli's discovery 

 of the weight of air not, indeed, until the time of the great pneu- 

 matic chemists, Black, Cavendish, Priestley, and Scheele was it ever 

 imagined that the aerial state, like the solid or liquid state, was a 

 state common to many distinct kinds of matter; and that the weight 

 or substance of a rigid solid might be largely contributed to by the 

 weight or substance of some constituent having its independent exist- 

 ence in the aerial or gaseous form. The notion that 100 pounds of 

 smithy-scales might consist of 73 pounds of iron and 27 pounds of a 

 particular kind of air, and that 100 pounds of marble might consist of 

 56 pounds of lime and 44 pounds of another kind of air, was a notion 

 utterly foreign to the elder philosophy. Air, it was allowed, might 

 be rendered mephitic by one kind of contamination, and sulphurous 

 by another, and inflammable by a third ; it might even be absorbed 

 in, and so add to the weight of, a porous solid, as water is absorbable 

 by sand ; but still air was ever indisputably air, essentially alike and 

 unalterable in its mechanical and chemical oneness. This familiar 

 conception had to be overcome, and the utterly strange notion of the 

 largely aerial constitution of solid matter to be established in its stead, 

 by the early pneumatic chemists, Black, Cavendish, and Bergmann, 

 before the deficiencies rather than positive errors of the phlogistic 

 theory could be perceived. 



But long ere the foundation of modern chemistry had thus been 

 laid, in 1756, by Black's discovery of fixed air or carbonic acid as a 

 constituent of mild alkalies and limestone, those old German doctors, 

 Beccher and Stahl, though ignorant of the nature of air, and neglectful 

 of the import of gravity, had yet found something to say about the 

 chemistry of combustion Avorthy of being defended a century after- 

 ward by men like Priestley and Cavendish worthy, it is believed, of 

 being recognized nearly two centuries afterward as the expression of 

 a fundamental doctrine in chemical and cosmical philosophy. They 

 pointed out, for example, that the different and seemingly unlike pro- 

 cesses of burning, smoiddering, calcining, rusting, and decaying, by 

 which combustible is changed into incombustible matter, have a com- 

 munity of character ; that combustible bodies possess in common a 

 power or energy capable of being elicited and used, whereas incom- 

 bustible bodies are devoid of any such energy or power ; and, lastly, 

 that the energy pertaining to combustible bodies is the same in all of 



