THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



AUGUST 1874. 



XIII. On Attraction and Repulsion accompanying Radiation, 



By William Crookes, F.R.S. <£&* 



[With a Plate.] 



BEFORE describing the apparatus and experiments which 

 illustrate the attraction and repulsion accompanying ra- 

 diation, it will perhaps be best to draw attention to the modifi- 

 cation of the Sprengel pump which has so materially assisted 

 me in this investigation. 



Fig. 1 (Plate I.) shows the pump as now in use. Working 

 so much with this instrument, I have endeavoured to avoid the 

 inconveniences attending the usual mode of raising mercury 

 from the lower to the upper reservoir. The mercury is con- 

 tained in a closed glass reservoir A, perforated with a fine hole 

 at the top. This reservoir is attached to a block capable of free 

 movement in a vertical line and running in grooves, and con- 

 nected with the lower reservoir by a flexible tube g. This tubing- 

 is specially made to stand a considerable pressure of mercury. 

 It consists of a double thickness of india-rubber tubing enclosing 

 a canvas tube in the centre, the whole being vulcanized together. 



When the whole of the mercury has run through the pump, 

 the reservoir and slide can be lowered by liberating a detent, T, 

 and letting it descend to the block L. II is a glass reservoir 

 which receives the mercury after flowing through the pump. 

 When the reservoir A is emptied and has been lowered to the 

 block L, the mercury from H is admitted into A by opening 

 the tap I. At/ is another tap, of platinum, to regulate the flow 

 of mercury through the pump. c } c, c' are mercury joints, it 



* A Lecture delivered before the Physical Society, June 20, 1874. Com- 

 municated by the Society. 



Phil. Mag. S. 4. Vol. 48. No. 316. Aug. 1874. G 



