188 NOVUM ORGANUM 



we will class those subjunctive instances, of which we spoke 

 in the last aphorism, and which we are also wont to call 

 instances of extremity or limits; for they are not only 

 serviceable when subjoined to fixed propositions, but also 

 of themselves and from their own nature. They indicate 

 with sufficient precision the real divisions of nature, and 

 measures of things, and the &quot;how far&quot; nature effects or 

 allows of anything, and her passage thence to something 

 else. Such are gold in weight, iron in hardness, the whale 

 in the size of animals, the dog in smell, the flame of gun 

 powder in rapid expansion, and others of a like nature. 

 Nor are we to pass over the extremes in defect, as well as 

 in abundance, as spirits of wine in weight, the touchstone 

 in softness, the worms upon the skin in the size of animals, 

 and the like. 



XXXV. In the thirteenth rank of prerogative instances 

 we will place those of alliance or union. They are such as 

 mingle and unite natures held to be heterogeneous, and 

 observed and marked as such in received classifications. 



These instances show that the operation and effect, which 

 is considered peculiar to some one of such heterogeneous 

 natures, may also be attributed to another nature styled 

 heterogeneous, so as to prove that the difference of the 

 natures is not real nor essential, but a mere modification 

 of a common nature. They are very serviceable, there 

 fore, in elevating and carrying on the mind, from differ 

 ences to genera, and in removing those phantoms and 

 images of things, which meet it in disguise in concrete 

 substances. 



For example: let the required nature be heat. The 

 classification of heat into three kinds, that of the celestial 

 bodies, that of animals, and that of fire, appears to be set- 



