( 58 ) 



g'teater convenience ifl use. The elastic hysteresis i) moreover is not 

 to be perceived, as is proved by the observations mentioned below. 

 The WoLLASTON wire of 25 /<, supplied by Hera us can bear but 4 

 grams, a platinum wire of 50 /< more than 30 grams ; most of the 

 later measurements have been made with this platinum wire. The 

 time of oscillation (Vg period) is about 12 sec, and as the damping 

 was so regulated that the needles were in rest after three oscillations, 

 the observation could already be made after 36 sec. 



In order to be able to regulate the damping, the hollow copper 

 cylinder is so long thinned and shortened, till (the whole iron core 

 being in its copper tube) the movement is aperiodic. By moving the 

 core downward, the required damping may be obtained. Every wire 

 has of course its own hollow copper cylinder which fits it best. 



In using the quadrant-electrometer the charging-battery is of great 

 importance. If measurements are to be made only for a short time, 

 a Zamboni pile or a battery of water-ceils, consisting of small 

 test tubes filled with water, in which copper and zinc rods have 

 been put, is sufficient. If the charging-battery, however, must be 

 kept ready for use for some months, these arrangements do not 

 suffice any more; nor have I succeeded in reaching this by 

 replacing the water by paste of plaster or by gelatine with carbol- 

 I was very much satisfied with 300 LECLANCHÉ-cells, supplied by 

 P. J. KiPP AND Sons, J. W. Giltat successor. In the following 

 measurements the positive pole of this battery was connected with 

 the needles, the negative one with the earth. 



Table I contains the comparison of six Clark-ccHs, constructed 

 according to the instructions given by Kahle in Wied. Ann. Bd. 51, 

 p. 203, 1894, with a normal Clark-ccU furnished by R. FuESS, 

 at Steglitz near Berlin and tested by the Physikalisch-Technische 

 Reichsanstalt. This cell is called N, while the cells, here constructed 

 are marked A, B, C, B, E and F. 



The negative pole of the cells remained connected with the earth, 

 the positive one with one of the pairs of the quadrants, while the 

 other pair of quadrants was kept on zero potential, the position of 

 equilibrium was determined. By reversal these two connections were 

 interchanged and this was continued till five observations were made. 



') Gekman: Elastische Kacliwirkung. 



