70 GAUSS AND WEBER ON TERRESTRIAL, MAGNETISM. 



2. Experiments of vibration. 



Consequently the time of one vibration t = 6"*67. 



3. Apjolication of the observations. 

 A general and intelligible view of the application of these 

 observations, without entering into theoretical considerations, 

 will be best given by exti'acting certain passages from a memoir 

 in Schumacher's Jahrbuch for 1836, entitled, " Ueber Erdmag- 

 netismus und Magnetometer ;" and adding the mathematical ex- 

 pressions of the laws there given verbally. 



*' The square of the number of vibrations made by a magnetic 

 needle in a given time, is a measure of the intensity of the earth's 

 magnetismwhich depends on the needle employed. The individual 

 properties of the needle have a two-fold influence : — first, by 

 the greater or less magnetic force which it possesses ; and se- 

 condly, by the effect of its form and weight on the time of vibra- 

 tion. The elimination of the latter effect presents no difficulty. 

 The influence of the earth's magnetism on the matjnetism of the 



