NOVUM OUGAMJM. 129 



thermometer is a conspicuous instance of the expansive 

 motion, which (as has been observed) constitutes the chief 

 part of the form of heat. For although flame clearly ex 

 hibit expansion, yet, from its being extinguished every mo 

 ment, it does not exhibit the progress of expansion. Boiling- 

 water again, from its rapid conversion into vapour, does not 

 so well exhibit the expansion of water in its own shape : 

 whilst red hot iron and the like are so far from showing 

 this progress, that, on the contrary, the expansion itself is 

 scarcely evident to the senses, on account of its spirit being 

 repressed and weakened by the compact and coarse particles 

 which subdue and restrain it. But the thermometer strik 

 ingly exhibits the expansion of the air as being evident and 

 progressive, durable and not transitory. 



Take another example. Let the required nature be 

 weight. Quicksilver is a conspicuous instance of weight : 

 for it is far heavier than any other substance, except gold, 

 which is not much heavier ; and it is a better instance than 

 gold for the purpose of indicating the form of weight. For 

 gold is solid and consistent, which qualities must be re 

 ferred to density, but quicksilver is liquid, and teeming 

 with spirit, yet much heavier than the diamond and other 

 substances considered to be most solid. Whence it is shown 

 that the form of gravity or weight predominates only in the 

 quantity of matter, and not in the close fitting of it. 



25. In the fourth rank of prerogative instances we will 

 class Clandestine instances ; which we are also wont to call 

 twilight instances. They are as it were opposed to the 

 conspicuous instances : for they show the required nature 

 in its lowest state of efficacy, and as it were its cradle and 

 first rudiments, making an effort, and a sort of first attempt, 

 but concealed and subdued by a contrary nature. Such 

 instances are, however, of great importance in discovering 

 forms, for as the conspicuous tend easily to differences, so 

 do the clandestine best lead to genera ; that is to those 

 common natures of which the required natures are only the 

 limits. 



As an example : let consistency, or that which confines 

 itself, be the required nature, the opposite of which is a 

 liquid or flowing state. The clandestine instances are such 

 as exhibit some weak and low degree of consistency in 

 fluids, as a water bubble, which is a sort of consistent and 

 bounded pellicle formed out of the substance of the water. 

 So eaves droppings, if there be enough water to follow 

 them, draw themselves out into a thin thread, not to break 



VOL. xiv. K 



