EXPERIMENTS WITH IONIZED AIR. 



By Carl Barus, 



HAZARD PROFESSOR OF PHYSICS AT BROWN UNIVERSITY. 



CHAPTER I. 



PRELIMINARY EXrERIMENTS. 



1. Color tube. — The apparatus for the observation of the colors of the cloudy 

 coudensatiou of water vapor in aii' will be briefly called the color tube or the steam 

 tube, as convenience suggests. In most of my earlier experiments it did not differ 

 essentially from the form devised aftei" loug trial in my previous papers ' on the sub- 

 ject. It will be necessary, however, to insert a shoi't description here, as otherwise 

 the account of many of the experiments given below would be unintelligible. 

 So too the condition under which steam-jet criteria are admissible will have to be 

 succinctly stated. 



The tube and appurtenances are shown in figures 1, 2, 3, and 4, the tube itself 

 in the first figure. Steam enters the tube A A directly by the jet j?, screwed into it 

 near the bottom. Air is supplied through G, which is of the same diameter as AA, 

 and B is the efilux. Sky light, Z, transmitted through the tube by means of the 

 adjustable mirror M, and the window a, is observed through the inclined plate g. 

 Here a difficulty presents itself, inasmuch as g at once clouds over ; but I eventu- 

 ally overcame this by moistening the inside of g with a solution of caustic potash 

 applied with a sponge probang through B. In this way a clear field is again 

 obtained foi- some time at least, after which the moistening must be renewed. The 

 inclined position of g makes the whole window easily accessible, and a special hole 

 closed by a cork may be cut in the elbow for inserting the probang when B is 

 otherwise engaged. Other tubului'es have special purposes, to be shown and stated 

 l:)elow. The windows ai'e suitably secured between rubber gaskets held in place by 

 flanges and bolts. 



The observer faces the plate g symmetrically and looks down the color tube 



' Cf. Condensation of Atmospheric Moisture, Bulletin No. 12, U. S. Weather Bureau, Washing- 

 ton, 189s, pp. 1-104. 



