relative to Black, Watt, and Cavendish. 507 



up with the air. Nor can we wonder that such an air, filled 

 with miasmata, if breathed by animals, cannot keep them alive, 

 especially when it is obvious that the spirit of nitre, and the 

 globule of iron, used by the distinguished author, abound in 

 many impure and poisonous particles, which if introduced into 

 the system in breathing, may well corrupt the mass of the 

 blood and induce death. If instead of the spirit of nitre he 

 had chanced to use another acid liquor of a more benign qua- 

 lity, for instance the spirit of vitriol, and instead of a globule 

 of iron, had taken one of an earthy kind, as in my experi- 

 ment, the animal doubtless would not have perished, or at 

 least would have lived longer. So that we may collect from 

 this, not that the air, as air, destroyed the animal, but only 

 incidentally, so far as it abounds with particles of a different 

 kind and unfit for the support of life. But that we may make 

 certain of one fact — namely that the substance of the globule 

 itself is not changed by the fermentation into air, but that air 

 really pre-existed in the globule, and was therefore not gene- 

 rated anew, the following experiment may be tried. Let the 

 weight of an earthy globule, well-dried, be taken with perfect 

 accuracy before the effervescence : then after the effervescence, 

 when all the particles of the globule subside to the bottom, 

 let the whole mass of the globule, which now lies dispersed, 

 be carefully re-collected from the liquor; and let it be well- 

 dried as before: lastly, let the weight-also of the dried mate- 

 rial be accurately ascertained by the help of the balance: this 

 done, we shall find that the substance of the globule has lost 

 nothing of its weight, or at least scarce a hundredth part, 

 which perhaps exhaled with the air during the effervescence. 

 But according to Mayow, it ought to have lost by far the great- 

 est part of its weight ; since it follows from his hypothesis, 

 that the whole body of air occupying the upper part of the 

 tube was taken from the substance of the globule ; and so its 

 weight should have been notably diminished, which neverthe- 

 less is contrary to experiment." 



In this criticism Bernoulli overlooked the chief fact on 

 which the theory of Mayow rested — the constant diminution 

 of the volume of common air, when breathed or burnt. And 

 his attempt at an experimental refutation of it may serve to 

 convince you of the danger which the greatest men may incur 

 when they venture on deciding chemical questions without a 

 knowledge of chemistry. To give the utmost credit to the 

 alleged result of his experiment we must presume the " acid 

 liquor" employed in it to have been oil of vitriol: but any boy 

 in a chemist's laboratory could have told him that the vitrio- 

 lated lime which he collected at the end of the experiment 



• 2 M 2 



