90 Mr. W. Crookes on Attraction and 



I may draw attention to the following experiments, which are 

 devised with the object of showing that the attractions and re- 

 pulsions are not due to electricity. 



In describing the pendulum apparatus (fig. 2) which I set in 

 motion at the early part of this lecture, I explained that the 

 mass of magnesium forming the weight was in metallic con- 

 tact with the platinum wire which supported it, and that the 

 upper end of this platinum wire was fused into the glass tube 

 and passed through to the outside. With this apparatus I have 

 tried a great number of experiments. I have connected the pro- 

 jecting end of the platinum wire with "earth/' with either pole 

 of an induction-coil the other being insulated more or less, with 

 either pole of a voltaic battery, with a delicate electroscope ; I have 

 charged it with an electrophorus, and have submitted it to the 

 most varied electrical conditions; and still, on allowing radiation 

 to fall upon the suspended mass, I invariably obtain attraction 

 when air is present, and repulsion in a vacuum. The heat has 

 been applied both from the outside, so as to pass through the 

 glass, and also inside by means of the ignited platinum wire ; 

 and the results have shown no difference in kind, but only in 

 degree, under electrical excitement. I have obtained interference 

 with the usual phenomena, but never of such a character as would 

 lead me to imagine that the normal results were due to electricity. 



It occurred to me that the repulsion might be due to a deve- 

 lopment of electricity on the inner surface of the glass bulb or 

 tube under the influence of the radiation as it passed from the 

 glass into the vacuum. This appears to be disproved by the 

 fact that the results are exactly the same whether the radiation 

 passes through the glass, or whether it is developed inside the 

 apparatus as in the above instance. 



I have produced exactly the same phenomena whether the 

 exhausted apparatus has been standing insulated in the air, or 

 whether it was completely immersed in water connected electri- 

 cally with " earth/' or surrounded with wet blotting-paper. 



Here are two experiments which bear on this subject. A 

 straw beam furnished with brass balls at each end is suspended 

 on a double-pointed needle, and the brass balls and needle 

 are placed in metallic connexion by means of fine platinum wire. 

 The needle does not rest on the sides of the glass tube, but in 

 steel cups, to which is soldered a platinum wire passing through 

 the glass tube and connected with "earth." The tube is then 

 exhausted, and the usual experiments are tried with hot and 

 cold bodies, both with and without a wet blotting-paper cover. 

 In all cases the moving beam behaves normally, being repelled 

 by heat and attracted by cold. 



An apparatus is prepared siniilai? %o that shown in fig. 4. 



