EXPERIMENTS WITH IONIZED A IK. 



into the third order. Von Hehiiholtz ^ saw all his coloi-s in the successive regions 

 of an open steam Jet, and reasonably inferred that the remote and cooler parts 

 contain the larger [)articles. Aitkeu's jets play into tubes. 



In my own work, most of the colors fi-om the browns of the first order to the 

 ci'imsons of the second could be pi'oduced in the tube, flgui'e 1, by simply decreas- 

 ing the pressure under which the steam is.sues from abt)ut 80 cm. of mercury to 

 zero, if the ingoing air is not too hot or cold. A much better method, however, 

 consists in using a copious steam efflux at very low pressure excess, and adding 

 unifoi'mly dusted air in the necessary amounts at 6' as will be instanced below. 



TABLE I.— SHOWING THE SUCCESSION OF COLORS. 



Between the brown and dark violet of the colors of the first order, there is an 

 opaque region. Sometimes the brown takes on a reddish hue and sometimes the 

 violet appears purplish : but the opaque region of indefinable color remains. In- 

 deed, it is a characteristic landmark in the color territory. Being absent in ex- 

 haustion it is to be interpreted with regard to the researches of Osborne Reynolds,'^ 

 on the flow of licpiids in pipes. Reynolds found that a colored jet passing through 



91 ; iVaiur,, XXXVII, p. 428, 1888; M./., XLI, p. 394, 189° ; '^'■'^- XLIV, p. 279, 1891 ; tW., 

 XlV p -99 1892, and elsewhere ; ^roc. Roy. Soc. Edin., LI, p. 425, (t seq., 1892. 



■'r. v. Helmholtz : Wied. Ann., XXVII, p. 508, 1886 ; ibid, XXXII, p. i, 1887. 



'Reynolds: I'hil. Trans., London, III, p. 935, 1883. 



