Knowledo;e. 



With which is incorporated Hardwicke's Science Gossip, and the Illustrated Scientific News. 



A Monthly Record of Science. 



Conducted by Wilfred Mark Welih. F.L.S.. and E. S. Grew, M.A. 



MARCH, 1011. 



X-RAYS. 



Bv REGINALD MORTON. .M.D. 



iCunfiiiiicd truiu Vulinnc XXXlll, piigc 49y.) 



Ix the course of an article in a previous number, the 

 development of some of the various i)arts that go to 

 make up a modern X-ray equipment was briefly 

 described ; of those' that remain to lie dealt with, 

 none have a greater importance than the interrupter, 

 or " break " as it is generally called. As its name 

 indicates, its function is to interrupt or break the 

 flow of current through the [)rimar\- coil of the 

 inductorium. A sudden 

 interruption is essential 

 for the working of the coil, 

 and the more sudden and 

 complete it is the better 

 is the discharge from the 

 coil. Up to the time 

 of Roentgen's discovery 

 breaks were of a simple 

 and not verv efficient 

 form; they were only useti 

 in circuit with batteries 

 of low voltage, and as the 

 induction coils were as a 

 rule small in size and giv- 

 ing short spark length they 

 answered well enough. 



The demand for greater 

 discharges to excite 

 heavier and stronger tubes 

 soon tnade it evident that 

 the interrupter would have 

 to be moditied, especially 

 as it was desired to make 

 use of the comparatively 

 high pressure currents 

 from the street mains. The 

 platinum hammer break iiy the comtcsy o/ 

 (see Figure 2) was one of Figure 1. 



the first, and though it is seldom used now for 

 hea\\- work, and mostl\- on portable apparatus, in 

 its most modern form it can be made to give very 

 good results. It requires care in adjustment and 

 manipidatidU. luit is practically the only kind that 

 can he used in military ser\ice in the field. 



.\ disad^•antage of this form is the flashing that 

 takes place' between the platinum points every time 



the current is broken; this 

 is troublesome when it is 

 desired to make use of 

 the fluorescent screen in 

 a dark room. 



It was found that when 

 the break \\ as so modified 

 that one of the points 

 was replaced by a dish of 

 mercur\-, the spark from 

 the coil was intensified.- 

 In one of the earliest types 

 a copper wire was made 

 to dip in and out of the 

 mercur}- by the action of a 

 small electric motor, and 

 a number of these are in 

 use, for X-ra\' treatment 

 especially. (See Figure 4.) 

 Following on this we 

 have the mercury jet 

 breaks, which were a great 

 improvement, in that they 

 gave a much higher rate of 

 interruption for the same 

 (|ualit\' of discharge from 

 the coil. In these a small 

 The Sanitas Ei<xt>k,ii Co. jct of mcrcury is made 

 \n .\-Kav Cabk-Testins' Outfit. to impinge upon a copper 



SI 



