NOVUM ORGANUM. 169 



be offered of abortions, animals killed in hunting, and the 

 like. Nature, therefore, must, as it were, be watched, as 

 being more easily observed by night than by day : for con 

 templations of this kind may be considered as carried on by 

 night, from the minuteness and perpetual burning of our 

 watch-light. The same must be attempted with inanimate 

 objects, which we have ourselves done by inquiring into 

 the opening of liquids by fire. For the mode in which 

 water expands is different from that observed in wine, vine 

 gar, or verjuice, and very different again from that observed 

 in milk and oil, and the like ; and this was easily seen, by 

 boiling them with slow heat, in a glass vessel, through 

 which the whole may be clearly perceived. But we merely 

 mention this, intending to treat of it more at large and 

 more closely when we come to the discovery of the latent 

 process ; for it should always be remembered that we do 

 not here treat of things themselves, but merely propose 

 examples. 



42. In the nineteenth rank of prerogative instances we 

 we will class Supplementary or substitutive instances, which 

 we are also wont to call instances of refuge. They are such 

 as supply information, where the senses are entirely defi 

 cient, and we, therefore, have recourse to them when appro 

 priate instances cannot be obtained. This substitution is 

 twofold, either by approximation or by analogy. For in 

 stance ; there is no known medium, which entirely prevents 

 the effect of the magnet in attracting iron, neither gold, 

 nor silver, nor stone, nor glass, wood, water, oil, cloth, or 

 fibrous bodies, air, flame, or the like. Yet by accurate 

 experiment, a medium may perhaps be found which would 

 deaden its effect, more than another comparatively and in 

 degree; as for instance, the magnet would not perhaps 

 attract iron through the same thickness of gold as of air, or 

 the same quantity of ignited as of cold silver, and so on : 

 for we have not ourselves made the experiment, but it will 

 suffice as an example. Again, there is no known body 

 which is not susceptible of heat, when brought near the 

 fire. Yet air becomes warm much sooner than stone. These 

 are examples of substitution by approximation. 



Substitution by analogy is useful, but less sure, and 

 therefore to be adopted with some judgment. It serves to 

 reduce that which is not the object of the senses to their 

 sphere, not by the perceptible operations of the impercep 

 tible body, but by the consideration of some similar per 

 ceptible body. For instance, let the subject for inquiry be 



