Shunt for alternate Currents of High Tension. 355 



tubular process is positive than to the reverse. lu some cases 

 this is sufficient to extinguish the discharge. Advantage was 

 taken of this fact, by using a tube furnished with several dia- 

 phragms, behind each of which was a terminal which exposed 

 a minute point of metal only. With a stronger current a 

 greater number of diaphragms was used in circuit ; with a 

 weaker current, a smaller number; and we were thus enabled 

 to adjust the resistance to the strength of current employed. 

 When several diaphragms were used the resistance became 

 very great. 



The Holtz tube, although in some ways very convenient for 

 use, is not without its drawback; for the narrow tubular pro- 

 cesses offer some (and not inconsiderable resistance) even to 

 the discharges which they allow to pass. This inconvenience 

 was obviated by substituting for the Holtz tube a column of 

 glycerine and water in which were inserted two terminals, one 

 consisting of a fine point and the other of a plate. The rod 

 which terminated in the point could be raised or lowered 

 according as it was required to increase or to diminish the 

 length of the column, and thereby the resistance employed. 

 By mixing the water and the glycerine in various proportions, 

 the resistance of the column could be varied within very wide 

 limits ; and by making the mixture as weak as possible com- 

 patibly with the requirements of the case, the instrument, or 

 electrical valve as it may be termed, could be made one of 

 extreme delicacy. 



The next step consisted in turning to account the set of 

 currents which had hitherto been merely shut off and not 

 utilized. The arrangement whereby this was effected will be 

 best understood by the diagram (Plate IX. fig. 1). A and B 

 are the two terminals of the coil; C and D, two glycerine-and- 

 water valves : E, a glycerine shunt ; F and Gr, two tubes, or 

 other passages for the currents. When the current, positive 

 at A, enters C, it passes through the valve to the tube F, 

 and thence to the opposite terminal B of the coil. When the 

 current is negative at A, it is unable to pass through the 

 valve C, and it is diverted to the tube Gr. The same current, 

 positive at B, passes through the valve D, also to the tube Gr. 

 The complete instrument may be called a separator. 



Thus far we have succeeded in separating the two sets of 

 currents, and in diverting one set, so as to make use of them 

 in a second tube or other channel. We have in fact disen- 

 tangled the two sets; but we have done this at the expence of 

 either making use of only one set, or at best of making use of 

 both in two separate tubes. It is, however, but seldom that 

 more than one tube is required at the same time for experi- 



