472 Resistance of Imperfectly Purified Sulphur. 



Deflexion of Galvanometer with fraction of current from large 



Clark Cell. 





Deflexion. 









Resistance 



taken out 



of S. 







Double 

 deflexion. 



Zero from 

 deflexion. 



Observed 

 zero. 







Right. 



Left. 









L. ohms. 



Divisions of 



Divisions of 



Divisions 



Divisions 



Divisions 



scale. 



scale. 



of scale. 



of scale. 



of scale. 



10 



+ 55 



+ 150 



95 



+ 103 



+ 105 



9 



+ 60 



+ 143 



83 



+ 101 



+ 103 



9 



+60 



+ 145 



85 



+ 101 



+ 103 



8 



+68 



+ 140 



72 



+ 104 



+ 103 



8 



+70 



+ 140 



70 



+ 105 



+ 103 



9 



+60 



+ 145 



85 



+ 101 



+ 100 



8 



+ 63 



+ 130 



67 



+ 96 



+ 90 



9 



+50 



+ 133 



83 



+ 91 



+ 90 



9 



+45 



+ 130 



95 



+ 92 



+ 85 



9 



+35 



+ 120 



85 



+ 77 



+ 80 



9 



+35 



+120 



85 



+ 77 



+ 80 



8 



+40 



+ 115 



75 



+ 77 



+ 78 



8 



+40 



+ 115 



75 



+ 77 



+ 80 



Rejecting those observations with the sulphur in which 

 the zero from the deflexions differs from the observed zero by 

 10. divisions and over, the mean double deflexion with a 

 current from 20 Clark cells sent through the sulphur is 85*5 

 divisions, and the mean deflexion with the current from the 

 large Clark cell when S = 9 ohms is 85*9 divisions. 



The difficulties which had to be met during these measure- 

 ments seemed to arise from what, following Mr. Bosanquet, we 

 at first called " ghosts." These phantoms, however, seem to 

 have arisen from people opening and shutting doors with iron 

 locks ; as a general rule the galvanometer was got properly 

 sensitive overnight, and it was found that if on the following 

 morning the light-spot was where it had been left, then the 

 observations were practically successful ; if, on the other hand, 

 the light-spot had gone off the scale, then there was not much 

 use in going on. The disturbance of the fibre consequent 

 on restoring the old zero did not seem to wear itself out 

 under at least twelve hours. It is practically impossible to 

 get a galvanometer of this degree of sensitiveness to work 

 with a silk fibre, the zero being always on the move. In 

 order to get rid of air-currents the ventilators of the room 

 required to be covered up, and the well-made galvanometer- 

 case had to be enclosed in a cardboard box. The insulation 

 at first gave great trouble. It is necessary to support the 



