580 HENRY A. ROWLAND 



they are homogeneous. Are they like light which can he divided up 

 into a large number of different wave-lengths, or are they homogeneous? 

 There seems to be a great deal of evidence that they are not all the 

 same; that one ought to get a spectrum of them in some way. We can 

 filter them a little bit through objects. After they are filtered through 

 an object, they are probably a little different from what they were 

 before, and some objects probably let through different rays from others. 

 In ' Nature ' Mr. Porter, I believe, has shown experiments upon that. He 

 divides rays into three kinds. At least he finds that under certain 

 circumstances the rays will penetrate bones better than in other cases 

 bones or any other object they have more penetrating power, and they 

 go through many of those objects that ordinarily stop them. By heat- 

 ing up the tube, and by various arrangements of his spark-gaps, etc,, 

 and putting little wires around his tubes, and so on, he can cause them 

 to generate different kinds of rays. That is a very important point, if 

 it is substantiated, and there seems to be little reason to doubt that a 

 number of rays really do exist; that whatever they are that come from 

 the object, they are not all the same; some of them penetrate bodies 

 better than others, and very likely some one will get up some sort of 

 filter that will filter them out, and allow us to use them and to find if 

 they have different properties. At the present we are rather in the 

 dark with regard to this point. 



Now I come to the theory of these rays. What is the cause of all 

 these phenomena? There was a time when we were rather self- 

 satisfied, I" think, with regard to theories of light. We thought that 

 Fresnel and others had discovered what light was some sort of vibra- 

 tion in the ether; we called it ether; if it had these, waves going through 

 it, then it would produce light, and we were pretty well convinced that 

 the waves were transverse, because we would polarize them; so that we 

 began to be satisfied that we knew something about light. Then Max- 

 well was born, and he proved that these rays were electromagnetic 

 very nearly proved it. Then Hertz came along and actually showed us 

 how to experiment with these Maxwell waves, most of which were 

 longer than those of light. At the same time they were of the same 

 nature. Well, we got a rather complicated sort of ether by that time. 

 The ether had to do lots of things. One must put upon the ether all the 

 communication between bodies. For instance, what communication is 

 there between this earth and the sun? Why, you have light coming 

 from it and heat. Radiation you might call it all. We have radiation. 

 Then some people thought they discovered electromagnetic disturbance 



