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- 

 damental methods or 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 



the death of Tobias Mayer. Gauss bestimmungen ' of the endeavour to 

 introduced Weber to his own exact i determine natural phenomena ac- 

 measurements of terrestrial magnet- cording to number and measure, 

 ism, and from hence Weber's own expressing surprise that this has 

 line of thought led through the not yet been done in electro- 

 phenomena of magneto - induction dynamics, and then proceeds to de- 

 (discovered by Faraday in 1831) . scribe his "electro-dynamometer," 

 and terrestrial magneto -induction an instrument used by him for 

 (1832) to electro - dynamics, the ; many years. With this instrument 

 science which Ampere had created he then, further, proceeds to con- 

 in the years 1820 to 1823. In 1846 firm Ampere's formula for the action 

 Weber speaks in the introduction ; at a distance of the elements of 

 to the ' Electro-dynamische Maas- electric currents. 



