50 DISCOURSE ON THE STUDY 



such, he is no longer content to limit his enterprises 

 to the beaten track of former usage, but is constantly 

 led onwards to contemplate objects which, in a pre- 

 vious stage of his progress, he would have regarded 

 as unattainable and visionary, had he even thought 

 of them at all. It is here that the investigation of 

 the hidden powers of nature becomes a mine, every 

 vein of which is pregnant with inexhaustible wealth, 

 and whose ramifications appear to extend in all di- 

 rections wherever human wants or curiosity may lead 

 us to explore. 



(43.) Between the physical sciences and the arts of 

 life there subsists a constant mutual interchange of 

 good offices, and no considerable progress can be 

 made in the one without of necessity giving rise to 

 corresponding steps in the other. On the one hand, 

 every art is in some measure, and many entirely, 

 dependent on those very powers and qualities of the 

 material world which it is the object of physical 

 enquiry to investigate and explain ; and, accordingly, 

 abundant examples might be cited of cases where 

 the remarks of experienced artists, or even ordinary 

 workmen, have led to the discovery of natural quali- 

 ties, elements, or combinations which have proved 

 of the highest importance in physics. Thus (to give 

 an instance), a soap-manufacturer remarks that the 

 residuum of his ley, when exhausted of the alkali for 

 which he employs it, produces a corrosion of his 

 copper boiler for which he cannot account. He 

 puts it into the hands of a scientific chemist for 

 analysis, and the result is the discovery of one of the 

 most singular and important chemical elements, 

 iodine. The properties of this, being studied, are 



