118 M. F. Kohlrausch on the Determination of the Absolute 



Fig. 2. 



same relative position and connexion 

 with two arms, k, of the middle disk, 

 which form with the former an exact 

 rectangular cross. In the drawing only- 

 one is visible. Each of these arms is 

 the metallic continuation of an arm at 

 right angles to it, as is seen in the ac- 

 cessory figure 2, which represents the 

 middle disk seen from below. This disk 

 has, moreover, an index which gives its 

 position in reference to the upper one. 



To the upper disk are fastened, first, the supports of the upper 

 hook e, and, secondly, two metal sectors of a ring, d, each forming 

 almost a semicircle. They are insulated from each other, but 

 are each screwed to one of the supports, e, so as to form a con- 

 ducting whole. Upon each of the half-rings there is a small metal 

 plate, by means of which one of the supports, c, can be kept fast 

 in any position in conducting communication with the ring. On 

 the external surface the half-rings are provided with a scale di- 

 vided into whole degrees, to which the previously mentioned 

 index points. 



The supports, e, have a hooked suspension above, with which 

 the whole is suspended to an axis, which is fastened to the bifilar 

 suspension (vide infra), as the lower one Fig. 3. 



is to the solenoid. Both axes are exactly 

 equal. Each consists of two parts, which 

 (as fig. 3 shows, of the natural size) are 

 firmly connected with, while insulated 

 from, each other. In this section also 

 the shaded part denotes vulcanite. 



This being premised, the path of the 

 electricity through the metallic parts of the suspension is easily 

 understood. A current entering at /passes through e, d, c, b to 

 a, then through the solenoid, and through a!, b\ c\ d f , e' to/'. 



The azimuth of the upper axis, and with it of the upper disk 

 and of all parts connected with it, is shown by the suspending- 

 wires. By turning the second disk the solenoid is placed in such 

 a position that a current traversing it does not alter the position 

 of rest. The plane of the coils of the solenoid is in this case 

 at right angles to the magnetic meridian ; hence it is only neces- 

 sary to effect the cross position of the lower disk by turning it 

 through 90°, to obtain the desired position of the plane of the 

 coils in the meridian. 



For the readings the rod s is provided with a mirror S, which 

 for distinctness' sake is represented on the side of the drawing. 



The bifilar suspension had to be different from the ordinary 



