NOVUM ORGANUM 133 



quicklime, when sprinkled with water, appears to conceive 

 heat, either from its being collected into one point (as we 

 observed of herbs when confined), or from the irritation and 

 exasperation of the fiery spirit by water, which occasions 

 a conflict and struggle. The true reason will more readily 

 be shown if oil be used instead of water, for oil will equally 

 tend to collect the confined spirit, but not to irritate. The 

 experiment may be made more general, both by using the 

 ashes and calcined products of different bodies and by pour 

 ing different liquids &quot;upon them. 



A negative instance may be subjoined of other metals 

 which are more soft and soluble; for leaf gold dissolved by 

 aqua regia, or lead by aqua fortis, are not warm to the touch 

 while dissolving, no more is quicksilver (as far as I remem 

 ber), but silver excites a slight heat, and so does copper, 

 and tin yet more plainly, and most of all iron and steel, 

 which excite not only a powerful heat, but a violent bub 

 bling. The heat, therefore, appears to be occasioned by 

 the struggle which takes place when these strong dissol 

 vents penetrate, dig into, and tear asunder the parts of 

 those substances, while the substances themselves resist. 

 &quot;When, however, the substances yield more easily, scarcely 

 any heat is excited. 



There is no negative instance with regard to the heat of 

 animals, except in insects (as has been observed), owing to 

 their small size; for in fishes, as compared with land ani 

 mals, a lower degree rather than a deprivation of heat is 

 observable. In plants and vegetables, both as to their 

 exudations and pith when freshly exposed, there is no sen 

 sible degree of heat. But in animals there is a great differ 

 ence in the degree, both in particular parts (for the heat 

 varies near the heart, the brain, and the extremities) and in 



