486 NOVUM ORGANUM. [BOOK IL 



iion into vapour, docs 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 strikingly 

 exhibits the expansion of the air as being evident and progres 

 sive, durable and not transitory. 1 



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 referred to density, but quicksilver is 

 liquid and teeming with spirit, yet much heavier than the dia 

 mond 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. 1 



XXV. In the fourth rank of prerogative instances we will 

 class clandestine instances, which we are also wont to call twi 

 light 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 



Bacon was not i*arc of the fact- since brought to light by 

 Kilmer, that down to fourteen fathoms from the earth s mean level the 

 thermometer remains fixed at the tenth degree, but that as the thermo 

 meter descends below that depth the heat increases in a ratio propor 

 tionate to the descent, which happens with little variation in all climates. 

 lUiffon considers this a proof of a central fire in our planet. Ed. 



1 All the diversities of bodies depend irpon two principles, i. e. the 

 quantity and the position of the elements that enter into their composi 

 tion. The primaiy difference is not that which depends on the greatest 

 &amp;gt;r least quantity of material elements, but that which depends on their 

 position. It was the quick perception of this truth that made Leibnitz 

 say that to complete mathematics it was necessary to join 

 ol quantity the analysis of position, #&amp;lt;& 



