48 GAUSS AND WEBER ON TERRESTRIAL MAGNETISM. 



tations in intervals of 10" (half of 20"), and even of /" (third of 

 21"). Some examples will best illustrate what further remarks 

 we may have to make. 



Observation on the l7 t/i August, 1836, /^r 10^ 20'. 



Ulrich. 



By Prof. 



The second column contains the several notations ; the third, 

 the partial results ; 870*80 is the mean between the first and third 

 notation, and therefore corresponds to \ii^ 19' 40", and so forth. 

 It is pleasing to perceive in this example, chosen from a time of 

 rapid change in the declination, how a practised observer can 

 recognize with certainty the changes occurring in 10 seconds. 



Observation on the 25th March, 1837, at 0^ 5'. 

 Goldschmidt. 



84800-) 

 848 05 [ 



By Dr. 



847 90 ! 

 84770J 



The first partial result in this case is obtained from the com- 

 bination of the first and fourth notations ; the second from that 

 of the second and fifth, &c. 



In this example the submultlple of the approximate time of 

 vibration is an integer number ; A\here this is not the case, the 

 time must be divided into unequal parts, which has, ho^\ ever, 

 no disadvantage, provided such an arrangement is made, that 

 the notations to be combined shall always have for the in- 

 terval to which they correspond the same approximate value of 

 the time of vibration, and that the time, and also its portions, 

 shall be registered. Thus, for instance, the observations in 

 the astronomical obseiTatory, with a bar of 25 pounds in weight, 

 having a time of vibration of 43*- 14, must be arranged according 



