RECENT WORK ON THE X RAYS. 105 



" 1. Black paper (sixteen leaves interposed). The collapse of 

 the gold leaves is immediate and complete in a few seconds ; they 

 do not rise again. 2. Plate of brass (two tenths of a millimetre 

 in thickness). No change in the divergence of the gold leaves. 

 3. Plate of alnminnm (one tenth of a millimetre). Immediate 

 fall, complete in a few seconds ; same result with plates of alumi- 

 num up to one millimetre, and even upward, and the Crookes tube 

 being removed to the distance of thirty centimetres. The sub- 

 stances easily traversed are silver in beaten leaves, leaves of 

 paper steeped in metallic solutions, vulcanized fiber, gelatin, cel- 

 luloid, ebonite, etc. The substances not traversed, at least in the 

 thicknesses employed, are brass, zinc, glass, and unglazed porce- 

 lain (three millimetres). Similar results have since been an- 

 nounced from several other investigators." 



A paper by G. Jaumann, under the title of Longitudinal 

 Light, is described in Nature: "It is based upon the law of 

 electric discharge enunciated by Jaumann in 1888, according to 

 which electric rays impinging at right angles upon a cathode 

 surface favor the dissipation of the charge upon it. Hence, the 

 writer argues, light vibrations must have a component in the 

 direction of propagation; they must, in fact, contain longitudi- 

 nal as well as transverse waves. It then becomes a question of 

 how Maxwell's electro-magnetic equations, which do not admit 

 of any but purely transverse vibrations, can be made to agree 

 with these conclusions. Jaumann gives a simple answer. Let 

 it be admitted that the specific induction capacity of a medium 

 and its magnetic permeability are affected by the oscillations 

 themselves. These 'constants' will then be variable, and when 

 introduced as such into the equations longitudinal vibrations are 

 at once seen to be possible. Each pencil of light will then be vi- 

 brating transversely along its center line, and toward the outer 

 edge the vibrations will become more and more longitudinal. The 

 author claims that this theory affords a natural and simple expla- 

 nation of a large number of discharge phenomena." 



Prof. Oliver Lodge, of University College, Liverpool, is reported 

 as having said that he felt inclined to adopt the view that the new 

 rays were longitudinal waves in the ether ; and that if this were 

 so the discovery would open up a department of physics as large 

 as light, sound, or electricity. Later, in a letter to Nature, dis- 

 cussing the theory of the anodal origin of the X rays, he says : 

 " The term ' anode rays ' for the rays discovered with so much 

 eclat by Prof. Rontgen, whether they be the same as those pre- 

 viously discovered by Dr. Lenard or not, is suggested by the 

 remarks of Mr. A. W. Porter at a recent meeting of the Royal 

 Society. They certainly do not start from the cathode, but from 

 some opposed surface a surface which may be an actual anode, 



