NOVUM ORGANUM 381 



We must make a more diligent inquiry into this instance ; for 

 herbs and green and moist vegetables appear to possess a latent 

 heat, so small, however, as not to be perceived by the touch in 

 single specimens, but when they are united and confined, so that 

 their spirit cannot exhale into the air, and they rather warm each 

 other, their heat is at once manifested, and even flame occasion- 

 ally in suitable substances. 



Here, too, we must make a more diligent inquiry ; for quick 

 lime, 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 pouring different liquids 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 whilst dis- 

 solving, no more is quicksilver (as far as I remember), but sil- 

 ver 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 bubbling. The heat, therefore, ap- 

 pears to be occasioned by the struggle which takes place when 

 these strong dissolvents penetrate, dig into, and tear asunder 

 the parts of those substances, whilst the substances themselves 

 resist. When, however, the substances yield more easily, 

 scarcely any heat is excited. 



There is no negative instance with regard to the heat of ani- 

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

 small size; for in fishes, as compared with land animals, 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 sensible degree of heat. But 

 in animals there is a great difference in the degree, both in par- 

 ticular parts ( for the heat varies near the heart, the brain, and 

 the extremities) and in the circumstances in which they are 

 placed, such as violent exercise and fevers. 



Here, again, there is scarcely a negative instance. I might 

 add that the excrements of animals, even when they are no 

 longer fresh, possess evidently some effective heat, as is shown 

 by their enriching the soil. 



Such liquids (whether oily or watery) as are intensely acrid 

 exhibit the effects of heat, by the separation and burning of 

 bodies after some little action upon them, yet they are not at 

 first warm to the touch, but they act according to their affinity 



