302 SMITHSONIAN MISCELLAN1;0US COLLECTIONS VOL. 52 



To show ionization : WSff2, 3, 4 and 5. 



To show mechanical action: Swififi and 3. 



To measure energy radiated: Wii(42o). 



With alkaline gases : SSffi and 2. 



For very slow rays: S2f i ; cf.Wh3(464), Ew3(3o8). 



Suggestions for Obtaining the Canal Rays. 



To obtain "Pure" Canal Rays, that is, to prevent cathode rays from "striking 

 back," thus obscuring the canal rays : 



1. Perforations in cathode must not be too large. The lower the gas 



pressure and the thicker the cathode, the larger they may be : 

 01(697,45); G3(20S) ; Ew3(298). With extreme vacuum, however, 

 cathode rays may appear: Wi(i7o); W3(446). 



2. Cathode rays may be bent aside with a weak magnet: 63(206); 



W5 (523,245). They may be distinguished from canal rays by their 

 magnetic or electrostatic deflection or by their charge : W5(523, 245) ; 

 or by fluorescence excited: G4(ii, loi). 

 To obtain "Slow" Canal Rays, even with high vacuum: 



1. An alloy of Na and K, or Ca may be used on cathode: Wh3(464) ; 



Ew3(307); Tm3(s62). 



2. Gas may be ionized by some other agent: 82(585); Wh3(464) ; 



Ew3(3o8). 

 Fluorescent Screen; a willemite screen is best: Tm3(562). 

 Pure Gas filling is necessary for some experiments. For precautions and 

 devices used see the following: 

 Hj. W4(423); WS(525, 255); W6(59i. Hittorf) ; SH(93) ; Fi(i54); 



813(28,407) ; 819(400) ; Ps2(248). 

 O2. W4(423); W5(525, 256); W8(66i) ; SH(93) I Ps3(26i). 

 He. Raui(422); Tm3(568). 

 Hg. W5(S2S, 255); 819(400). 



2. COLOR OF THE BUNDLES OF RAYS. 



In N or Air. Apparently bright chamois yellow : Gi (692, 696, 39, 44) ; 

 03(205). Due to diffuse secondary rays: 02(133); 06(229). 



Really bluish- Bgi(695); G2(i33) ; G6(229) ; Kn3(37). 

 In Oj. Yellow-pink: 01(696, 44). Turns bluish as potential rises: Ps4(999) ; 

 In Ha. Rosy: 01(696, 44). Color very sensitive to impurities in gas, is red 



for pure H: 813(28, 407). 

 In Ha and Na vapor. Brilliant sodium yellow: 88(459). 



In Hi and K vapor. Beautiful violet like potassium Bunsen flame: 88(460). 

 In CO2. Greenish gray, white: 01(696, 44). 

 In N2O. Momentarily gray, becomes blue in 5 sec: Kn3(37). 

 In illuminating gas. Gray: Kn3(37). 

 In General.— Color is the same as that of first cathode layer: 01(696, 44). 



Color is independent of the material of cathode: 01(697, 45). 



Color depends to some extent on velocity: 810(254); 823(811). 



