62 STATE OF EMPIRICAL KNOWLEDGE, AND 



stmetion of matter by a combination of molecules and atoms 

 whose number, form, position, and polarity, determine, 

 modify, and vary the pheenomena. The suppositions of im- 

 ponderable matter, and vital forces peculiar to each mode of 

 organization, have complicated and perplexed the view. 

 Meanwhile, the prodigious mass of empirical knowledge is 

 enlarging with increasing rapidity ; and investigating reason 

 tries at times, with varying success, to break through ancient 

 forms and symbols invented to effect the subjection of 

 rebellious matter to mechanical constructions. 



We are yet very far from the time, even supposing it 

 possible that it should ever arrive, when a reasonable hope 

 could be entertained of reducing all that is perceived by 

 the senses to the unity of a single principle. The complica- 

 tion of the problem, and the immeasurable extent of the 

 Cosmos, seem to forbid the expectation of such success in the 

 field of natural philosophy being ever achieved by man ; but 

 the partial solution of the problem the tendency towards a 

 general comprehension of the phenomena of the universe 

 does not the less continue to be the high and enduring ai}ii 

 of all natural investigation. For my own part, faithful to the 

 character of my earlier writings, and to that of the labours 

 which have occupied my scientific career, in measurements, 

 experiments, and in investigation of facts, I limit myself in the 

 present work to the sphere of empirical conceptions. It is 

 the only ground on which I feel myself able to move without 

 a sense of insecurity. This mode of treating an aggrega- 

 tion of observed facts does not exclude their combination by 

 reasoning, their arrangement under the guidance of leading 

 ideas, their generalisation wherever it can be justly effected, 

 and the constant tendency to the discovery of laws. A 



