528 MEMOIR OF KIRCHHOFF. 



riite, just because the technics of pure logical thiiikiug have to be de- 

 veloped to a great extent, the perceptive faculty of a mathematician, 

 his judgment and his representation of things are of a peculiar kind. 



The natural philosopher requires however another faculty still, 1 

 mean the faculty of observation. Every one whose work rests on ob- 

 servation is a student of nature in the widest meaning of this word ; 

 the physician, the traveller, the collector. To observe is to notice, and 

 to collect what you have noticed. In proportion however as the col- 

 lecting of things is done according to higher and higher standards, ob- 

 servation comes nearer to thinking, collecting approaches interpreta- 

 tion, and natural history verges into exact study of nature. The 

 adepts of natural science work not only through the senses by means 

 of observation, but also by means of the logical faculty of drawing In- 

 ference. They differ from mathematicians chiefly in tbe material for 

 their thinking being given in the external world and that they must 

 have the talent to find it there, while the foundations of mathematics 

 seem to be giv^en a 'priori. Mathematics is the most convenient instru- 

 ment in the exact science of nature because it is the tongue in which 

 the latter can express its conclusions in the quickest and most precise way. 

 That is why the exact study of nature becomes more and more mathe- 

 matical ; physics, after astronomy, has made the most progress in this 

 direction; chemistry is about to follow it. Speaking generally, the 

 greatest physicist nowadays will be he who is endowed equally with the 

 gifts of observation and with logical precision of thinking, and has mas- 

 tered experiment as well as mathematics. According to the pre-emi- 

 nence of the one or the other faculty the place of each investigator 

 will be nearer to the observers of nature or to the thinkers about nat- 

 ure. Both kinds are necessary, the latter is more seldom met with, 

 there are more good observers than good thinkers. Gustav R. Kirchhoff 

 belongs rather, according to his nature, to the great thinkers, and still 

 his greatest and most celebrated discovery is a discovery of observa- 

 tion. He was one of the greatest natural philosophers just because he 

 was a mathematical physicist in the above-mentioned sense. 



The life of Kirchhoff was that of a thinker, too. He did not travel 

 all over the world to see nature in the splendid attire of her multifari- 

 ous productions, like Humboldt or Darwin; he did not work his way to 

 theory through a school of purely practical life, like Faraday or Siemens. 

 No more did he pass his life in the whirlpool of historical or social 

 events. He accomplished his work quietly in the externally serene, 

 but internally the more active, abodes of science, — in the lecture-rooms 

 and laboratories of several German universities. Whoe\"er wants to 

 know him must follow him thither into spheres of thought that lie afar 

 off" from the interests of the day. 



Gustav K. Kirchhoff", sou of the lawyer, was born (1824), brought up, 

 and educated at Kiinigsberg, the " City of Pure Reason." According to 

 a certificate from the Kneii)hof High school, he wished to devote him- 



