578 HENRY A. EOWLAND 



rays strike on the anode. However, that is a point of discussion. Now, 

 as to the source of electricity, we have generally the Euhmkorff coil. 

 There is one source of which I saw a little note in ( Nature,' where a 

 man had used a large Holtz machine with very good effects. Now it is 

 very much easier for many persons to use a Holtz machine than to use 

 a Euhmkorff coil. There are many cases where one cannot have a large 

 battery; and this man said that with the Holtz machine he got as great 

 an effect as with the Euhmkorff coil. Then we have the Tesla coil, etc. 

 By the way, speaking of the Tesla coil, I am not sure but that you 

 might look back and find that it is very similar to the Henry coil. 

 Henry originally experimented on the induction of electricity, transmit- 

 ting a spark of electricity from one coil and getting a spark from an- 

 other, and the Tesla coil is something like that, except that it is made 

 so as to produce a much more voluminous spark. 



We all know the properties of the Eontgen rays they go in a straight 

 line. Every effort to deviate them from a straight line, by any means 

 whatever, has failed, except that when they strike upon an object they 

 are reflected. Now, it is a question for discussion as to whether there is 

 any regular reflection. They strike upon an object, and you get some- 

 thing from that object which will affect a photographic plate. Are 

 those rays which you get from the object Eontgen rays still, or do the 

 Eontgen rays strike upon this object and generate in it some sort of 

 rays which come out, different from the Eontgen rays, and affect the 

 plate? We do not know that. Neither are we quite positive whether 

 there is any reflection of the rays. We know there is turbid reflection 

 you may call it rays strike on the object, and the object becomes a 

 source of rays of some kind. Nobody has ever found out what sort of 

 rays come from the object. Something comes from it, and we generally 

 imagine, and indeed we often state, that they are Eontgen rays that 

 come off the object. But we have good reason to suppose that they 

 may be something else; and they may or may not be regular reflections; 

 some persons say they are and some that they are not. I have seen 

 some photographs made in this city which indicated regular reflections. 

 At the same time I would not be positive as to whether there was any 

 regular reflection. It is rather doubtful. It is a point to be determined. 



Then the fluorescence that is the way Eontgen originally found the 

 ray. You know the way they produce fluorescence the photographic 

 effect you all know that. You all know that the magnet does not 

 affect them does not turn these rays from a straight line. 



The polarization of the rays: We have no evidence whatever as to 



