Minutes of Proceedings. xiii 



African College, the results of which would be communicated to the 

 Society in due course. A tube of the most recent type had been 

 ordered, which, in conjunction with the induction coil belonging to 

 College, would enable all the Eontgen experiments to be performed 

 at an early date. 



Dr. Mum said that six names were to him of most importance in 

 the history of the discovery — those of Maxwell, Hertz, Crookes, 

 Leonard, Eontgen, and Becquerel. 



Mr. Trotter said that Professor Holm and he had been making 

 some attempts to produce Eontgen photographs by means of calcium 

 tungstate under the influence of concentrated sunlight, but the 

 experiments had so far been unsuccessful. Professor Hahn had 

 prepared some calcium tungstate, but it appeared that the salt 

 should be crystallised in a special manner in order to give the best 

 results. 



The most general hypothesis at that date was that Eontgen rays 

 were longitudinal vibrations, and there were reasons for supposing 

 that the velocity of propagation was very great, and that the wave- 

 length also was very great. A wave-length of ordinary light was 

 about one fifty-thousandth of an inch. The present method of 

 producing light was a most barbarous one, and was to be compared 

 to depressing all the notes from the bass upwards of an organ in 

 order to produce a few shrill notes. The present mode of producing 

 light was to raise a body to white heat, and all the lower vibrations 

 of heat were wasted. Some day, however, light would be produced 

 without heat. This secret is known only to the glow-worm and the 

 firefly, and it seemed possible that these creatures would be found 

 to emit Eontgen ra/ys, since there appeared to be a connection 

 between fluorescence and phosphorescence and Eontgen action. 



Vibrations producing radiant heat were longer than those pro- 

 ducing light, but the vibrations discovered by Hertz were much longer. 

 They were of the same nature as light but were invisible. Such 

 rays consisting of vibrations a yard long would traverse a brick wall. 

 Low musical notes, too, could penetrate a wall which stopped higher 

 notes. It seemed likely, then, that Eontgen rays were of considerable 

 wave-length. If this were so their velocity must be great, and a 

 most important question arose whether there could be any connection 

 between these rays and gravitation. Gravitation appeared to act 

 instantaneously — but instantaneous action at a distance was almost 

 unthinkable. The velocity would have to be very large. Even if it 

 were one million times faster than light, it would occupy as much 

 time to act between the earth and the sun as light would take to 

 travel ninety-two miles. This would produce effects of aberration 



