CROOKES'S ULTRA-GASEOUS STATE OF MATTER. 



Messrs. Mawson and Swan, of Newcastle-on-Tyne, are prepared to supply 

 the following Vacuum-Tubes, illustrating Mr. Crookes's recent researches on 

 the ultra-gaseous state of matter. 



1.— THE ELECTRICAL RADIOMETER. 



Showing the dark layer of freely vibrating molecules by which, on Mr. Storey's 

 theory, the rotation is effected. The exhaustion of this bulb is rather higher 

 than that of ordinary vacuum-tubes. 



2.— THE CUP ELECTRICAL RADIOMETER. 



This Radiometer consists of four hollow cups like an anemometer : when con- 

 nected with the induction-coil it rotates, concave side forwards, just as the cup 

 Radiometer does under the influence of light or heat, the molecular streams 

 being converged on the concave, and expanded on the convex side, so as to 

 react against the glass envelope. 



3.— THE BLUE FOCUS. 



A concave reflector at moderate exhaustion, showing the remarkable appear- 

 ance of a luminous focus in an " optically pure " vacuum without the presence of 

 any solid matter or floating particles. 



4.— THE GREEN FOCUS. 



This bulb is almost absolutely vacuous. At this extreme exhaustion the mo- 

 mentum of the molecules is expended on the glass, which becomes fluorescent at 

 ' the focus and very hot. 



5.— THE MOLECULAR SHADOWS. 



A highly exhausted bulb containing a cross formed of glass at its centre. The 

 molecules impinging on the surface of the glass render it fluorescent, except 

 where diverted by any solid object placed in their path. Hence apparently 

 black shadows of glass figures are projected on the bulb; and if the molecules 

 are caused to alter their path by bringing a magnet near to the tube, the sha- 

 dows are twisted out of their position. 



Messrs. Mawson and Swan are also prepared to supply the following tubes, 

 illustrating Mr. Orookes's latest experiments on Phosphorescence in high 

 vacua: — 



(1) Ruby. — A mass of rough rubies exposed to the action of the negative- 

 pole discharge of an induction-coil glows with a magnificent carmine light. 



(2) Sapphire. — Red and bluish-grey light, polarized. 



(3) Diamond. — Light blue colour; varies with the locality from which ob- 

 tained. 



(4) Tinstone. — Yellow light, polarized. 



(5) Emerald. — Crimson light, polarized. 



(6) Sulphides of Barium, Strontium, Calcium, &c. — These all glow with 

 marvellous brilliancy under the action of the negative-pole discharge of an in- 

 duction-coil. ' 



Others in preparation. 



MAWSON AND SWAN, Newcastle-on-Tyne. 



Now ready, price Is. 



ON SOME POINTS IN THE THEORY OF THE INFINITE AND OF 



INFINITESIMALS. 



By ROBERT MOON, M.A., 



Honorary Eellow of Queens' College, Cambridge. 



Taylob and Feancis, Red Lion Court, Fleet Street, E.C. 



[ADVERTISEMENTS cm^tinued on 3rd page of Covet. 



