368 SCIENTIFIC THOUGHT. 



different electric phenomena those of electricity in the 

 state of rest, called statical effects ; those of electric 

 currents on each other, the dynamical results ; and those 

 of electric conductors in a state of motion, the pheno- 

 mena of induction in one general and fundamental 

 formula or law. He had before him Coulomb's electro- 

 static formula, Ampere's electro- dynamic formula, and a 

 more general one established by Franz Neumann, which 

 described and embraced not only the phenomena dis- 

 covered by Oersted, but also those of moving conductors 

 discovered by Faraday. It is not necessary here to enter 

 into the details of the investigations, experimental and 

 mathematical, by the aid of which Weber succeeded in 

 establishing his very remarkable and seemingly all- 

 embracing formula. Two remarks, however, present 

 themselves, bearing upon the history of thought and the 

 value of precise mathematical expressions. The first is, 

 that as the gravitation formula necessitated a series of 

 the most careful definitions and measurements of physical 

 ss. quantities, and the invention of accurate instruments and 



Weber's fun- i -i r- 



damentai methods of measurement, so the first and probably the 



measure- 



ments, most valuable performances of "Weber were his ingenious 

 apparatus, and the careful measurements by which he 



bestimmungen ' of the endeavour to 



the death of Tobias Mayer. Gauss 

 introduced Weber to his own exact 

 measurements of terrestrial magnet- 

 ism, and from hence Weber's own 

 line of thought led through the 

 phenomena of magneto - induction 

 (discovered by Faraday in 1831) 

 and terrestrial magneto -induction 

 (1832) to electro - dynamics, the 

 science which Ampere had created 

 in the years 1820 to 1823. In 1846 

 Weber speaks in the introduction 

 to the ' Electro-dynamische Maas- 



determine natural phenomena ac- 

 cording to number and measure, 

 expressing surprise that this has 

 not yet been done in electro- 

 dynamics, and then proceeds to de- 

 scribe his "electro-dynamometer," 

 an instrument used by him for 

 many years. With this instrument 

 he then, further, proceeds to con- 

 firm Ampere's formula for the action 

 at a distance of the elements of 

 electric currents. 



