Si II V< / GOSSIP. 





irrei will reaterwil 



. 

 form 

 It will b n t i tab] 



mew for com n up different Id p 



F CJnivbrsai I. \mi- Rbsistanci 



parallel] 01 both, required values of current can be 

 tined. Two convenient instruments for this 

 purpose arc- shown in figs. 15 and 16. In the former 

 of these, two brass trips 

 run parallel down the 

 length oi hi base, and 



arc eai 1 lected 



one of the termin 1! 



Between these strips 



are fitted lamp holders, 



so thai by inserting a 



lamp in anj one ol them 



the circuit is compli ted 



through that lamp, and 



.1 certain strength of 



1 in rem passes. Two 



lamps of the same c.p. 



inserted will double the 



current, for they will be 



running in parallel. Each additional lamp in 



the current, and the form shown in fig. 15 will 



take six lamps thus arranged. 



Fig. 17. Ammeter-Voltmeter, 



F10. 18. Ft 1 oroscope Extended. 



In older to widen the application of these lamp 

 binations, a different set of connections may be re- 

 sorted to, as is shown in lit;. 16. Herethe lampsockets 



top of 

 ily bridging 

 cross by 1 



irallel, 



... 1 



1 1. bo 



m in the strength 

 by having 



candli 



01 

 lance shown in fie;. 1 

 provided with a zinc box in 

 which the lamps hang. Thi 

 serves :i do bli 

 by filling it with water thi ii 



ment may be kepi 1 1 ; secondly, 



il shields the sui from 



the lighl ofthe lamps ,1 desidera- 

 tum, especially whend 



. 1] .1. \ Ray work. Water resi tanci m I 



as a third variety, to cut down the current 

 required values, but they are generally not so con- 

 nil hi or so cheap as the other two forms. 

 In addition to a proper resistance an X-Raj 

 will not he complete without a voltmeter, and an 

 ammeter, with which to met potential and 



current respectively — especially if the supply from the 

 mains is used. These instruments are made in 

 various forms, either for use in a vertical or a hori- 

 zontal position. One of the former patterns is 

 shown in fig. 17. 



1 nnecting up these instruments in circuit, the 



ammeter is placed in series with the source ol supplj 



and the induction coil, hut the voltmeter is ted 



as a shunt across the terminals of the coil and break, 

 and should not lie allowed to remain in circuit 

 permanently. 



Before leaving the subject of the mains supply 

 current, a few more words max lie said upon the use 

 of the Wehnelt break already described (ante, p. 202). 

 It has been asserted that this break may be con- 



Fig, 19. Fluoroscope Cu isi r>. 



necled with a coil direct to the continuous supply 

 terminals, and without any intervening resistance. 

 Unless, however, the operator is quite easy in his 



