EXTRACT XIII. 



SUMMARY OF STUDIES ON CIRCULATION. 



" All things flow, and nothing is at rest." 

 " All things are in a state of flux." 



THE author of these words was the Greek philosopher 

 Heraclitus, who lived about 500 B.C. The law enun- 

 ciated, and the generalisation accomplished, in them 

 necessarily presuppose the possession, by their author, 

 of a knowledge of " first principles," derived from a wide 

 range of observation of natural phenomena, and a grasp 

 of their significance which can scarcely be surpassed, or 

 paralleled in the whole history of, at any rate, ancient 

 natural science. In the terseness of their expression, and 

 arrangement, and in the depth of their meaning, we see 

 one of the most successful attempts to reach the bed-rock 

 of natural truth^ as we may call it, and to lay for ever on it 

 a foundation which could bear the weight of the most 

 gigantic superstructure, and which could yield security 

 for the exercise of the best efforts of the votaries of 

 science, and make a worthy repository for their contribu- 

 tions to the sum of human knowledge. 



The principal truth conveyed by them is, that matter, 

 in its widest, as well as, most restricted sense, in mass, 

 and in molecule, is ever moving, that a state of flux and 

 re-flux characterises the behaviour of the material universe, 

 and that no possible exception is to be perceived within 

 the sphere, sidereal, or terrestrial, of its application. 



