84 DISSERTATION SECOND. lpart i. 



and unceasing action. ' The desire of making observation 

 easy is the great source of this propensity. Men wish for 

 knowledge, but would obtain it at the least expense of 

 time and labour. As there is no time, however, at which 

 the hand of nature ceases to work, there ought to be none 

 at which observation ceases to be made. 



The instantiae persecantes, or vellicantes, are those 

 which force us to attend to things which, from their sub- 

 tilty and minuteness, escape common observation. 



Some of Bacon's remarks on this subtilty are such as 

 would do credit to the most advanced state of science, and 

 show how much his mind was fitted for distinguishing and 

 observing the great and admirable in the works of nature. 



The last division contains seven classes, of which I men- 

 tion only two. The experiments of this division are those 

 most immediately tending to produce the improvement of 

 art from the extension of science. " Now there are," says 

 Bacon, "two ways in which knowledge, even when sound 

 in itself, may fail of becoming a safe guide to the artist, and 

 these are either when it is not sufficiently precise, or when 

 it leads to more complicated means of producing an effect 

 than can be employed in practice. There are therefore 

 two kinds of experiments which are of great value in pro- 

 moting the alliance between knowledge and power ; — those 

 which tend to give accurate and exact measures of objects, 

 and those which disencumber the processes deduced from 

 scientifick principles of all unnecessary operations." 



In the instantiae radii we measure objects by lines and 

 angles ; in the instantiae cnrriculi by time or by motion. 



To the former of these classes are to be referred a num- 

 ber of instruments which now constitute the greater part of 

 the apparatus of natural philosophy. Though Bacon had 



1 Nov. Org. II. Aph. 41. 



