GAUSS AND WEBER ON TERRESTRIAL MAGNETISM. 3/ 



buildings, a positive conviction may be acquired, that their in- 

 fluence on each other is harmless, or, if this should not be the 

 case, that their effect may be reduced to calculation. 



Explanation of Finite X. 



In this plate the several parts of the magnetometer are repre- 

 sented, with the exception of the clock, theodolite, measuring 

 scales, the box, the torsion and quieting bar, which partly require 

 no particular representation, and in part have been already shown 

 on a smaller scale, in Plates II. and III. On the other hand, the 

 arrangement of the suspender with the elevating screw, the stirrup 

 with the torsion-circle, the mirror-holder, with its corrections, 

 the weights and the weight-holder, stand in need of a more 

 accurate representation, which is given from various sides in 

 this plate, on a scale of half their actual magnitude. The stir- 

 rup, the torsion-cu'cle, and the magnet bar in its place, have 

 been represented in three different positions — from the west, 

 from the south, and from above ; the mirror-holder, and the 

 suspender, with the elevating screw, have been figured from two 

 sides — from the west, and from the south. In the south view 

 of the stirrup, with the torsion-circle and the magnet bar in its 

 place, is shown the manner in which the weight-carrier may be 

 placed on the magnet bar in a west and east dii'ection, and the 

 two weights, each of half a kilogramme, suspended to the points 

 with which it is furnished, for the purpose of determining, in 

 absolute measurements of intensity, the moment of inertia of the 

 ^dbrating portion of the magnetometer. To spare room on the 

 plate, the two views of the bearer, with the elevating screw, 

 have been placed in the upper series, close to one another, but 

 this has prevented the bringing of the two into the correct posi- 

 tion relatively to the ^'ibrating portion of the magnetometer sus- 

 pended from them. It is, however, easily seen how the view of 

 the suspender, with the elevating screw in fig. 1., is connected 

 with that of the stirrup, torsion-circle, magnet bar, and mirror- 

 holder in fig. 3. if we attend to the commencement indicated in 

 fig. 1. and the teraiination indicated in fig. 3. of the vertical hne 

 connecting them. These two tigures represent the main parts of 

 the magnetometer in a westerly view. In the same manner fig. 2. 

 and fig, 6. are connected, and represent the instrument as observed 

 from the southern position. In fig. 6. the muTor-holder has been 

 taken off from the southern extremity of the magnet bar, so that 



