332 NOVUM ORGANUM. 



transparency follows the same conditions as the Instances men 

 tioned above. 



xxiv. Among Prerogative Instances we shall put in the third place, 

 Ostensive Instances, of which we have made mention in the First 

 Vintage concerning Heat, and which we also call Glaring, or Liberated 

 and Predominating Instances. They are those which show the Nature 

 in question in its bare and substantive condition, and also in its 

 exaltation, or highest degree of power, as being emancipated and 

 freed from impediments, or at least triumphing over them, and by 

 virtue of its influence suppressing and coercing them. For since 

 every body contains in itself many copulate Forms of Natures in the 

 concrete ; it follows that they severally drive back, depress, break, 

 and bind one another ; and hence the individual Forms are obscured. 

 But there are found some subjects in which the required Natures 

 surpasses others in vigour, either through the absence of impediment, 

 or the predominance of its own virtue. And Instances of this kind are 

 the most Ostensive of Form. But in these Instances also we must 

 be cautious to restrain the impetuosity of the Understanding. For 

 whatever displays the Form, and seems to intrude it upon the Under 

 standing, must be looked upon with suspicion, and recourse must be 

 had to severe and diligent Exclusion. 



For example : suppose the Nature inquired into to be Heat. The 

 aerial heat-glass is an Ostensive Instance of the motion of expansion, 

 which (as has been said above) is the principal part of the Form of 

 Heat. For flame, though it manifestly exhibits expansion, yet, owing 

 to its momentary extinction, does not display the progress of expan 

 sion. And hot water, owing to the easy transition of water into vapour 

 and air, does not so satisfactorily display the expansion of water in its 

 own body. Again, ignited iron, and the like, are so far from display 

 ing this progress, that, from the repercussion and breaking up of their 

 spirit by the compactness and density of their parts (which tame and 

 bridle the expansion), the expansion itself is not at all conspicuous to 

 the senses. But the heat-glass clearly shows expansion in air, and 

 that, too, conspicuous, progressive, durable, and not transient. 



To take another example : let the Nature inquired into be Weight. 

 Quicksilver is an Ostensive Instance of Weight. For it surpasses 

 everything in weight by a very long interval, except gold, and that is 

 not much heavier. But quicksilver is a better Instance for indicating 

 the Form of Weight than gold, because gold is solid and consistent, 

 properties which seem to relate to density ; but quicksilver is fluid, 

 and charged with spirit, and yet it far exceeds in weight the diamond 

 and those bodies which are thought to be the most solid. Whence 

 it is demonstrated that the Form of Weight predominates simply in 

 quantity of matter, and not in compactness of frame. 



xxv. Among Prerogative Instances we shall put in the fourth place 

 Clandestine Instances, which we also usually call Twilight Instances. 

 They are as it were, opposed to Ostensive Instances. For they exhibit 

 the Nature under investigation in its lowest degree of influence, and, so 

 to speak, in its cradle and first rudiments, striving to make a sort of 



