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THE ROYAL SOCIETY OF CANADA 



over the roller L, down in front of drum Q, between the friction rollers 

 not shown, on to the storage drum S, where it can be fixed by inserting 

 the end of the paper in a slot provided for it. The spindle of S, is pro- 

 vided with a cord the end of which can be fixed in any convenient posi- 

 tion under the case. A weight and pulley, not shown, are then sus- 

 pended on this cord, thus exerting a turning movement to the drum 

 and keeping the paper taut while passing through the instrument. In- 

 stead of using charts ruled with a time scale, blank forms are used and 

 the time is given by an arrangement which brings a small rod under the 

 depressor bar for about 6 minutes before the hour. This rod gives a dot 

 near the edge of the chart every two minutes while it is under the bar, 

 and it is so adjusted that the last dot of the series gives the hour mark. 

 These marks are shown on the chart. 



Suspension. 



Phosphor bronze suspensions are employed in the usual manner 

 and it is found that wire 0-002 " diameter gives good stability. 



Automatic Zero. 



The drum Q. makes two revolutions in 25 hours, and advantage 

 was taken of this to attach an arrangement whereby the needle was 

 earthed for about 12 minutes, during each revolution of the drum. 

 The zero position is thus automatically given twice a day. 



Results. 



Fig. II gives an actual trace of the instrument for a leakage test. 

 This shows that the insulation is of a very high order. 



Table III gives some of the tests made on the sensibility. One 

 pair of quadrants was connected to the positive terminal of the battery 

 the other pair to the negative and the centre of the battery was earthed 



Table III. 



A=^Potential difference of quadrants x Volts per mm. deflection. 



