On Change of the Colours of Cloudy Condensation. 573 



AA being a hollow conoid about 5 centims. long and 9 

 centims. internal diameter, provided with a side tnbulure, T, 

 conveying the steam from the steam-box. The body being 

 open above and below, receives the hollow spindle, BC, 

 axially, the latter being secured in any position by the 

 snugly-fitting screw at C. The top, B, of the spindle is 

 ground into the upper aperture of the body like an ordinary 

 screw-valve, so that steam may be quite shut off or supplied 

 in any reasonable quantity, at any pressure, by turning the 

 head of the spindle at C. 



The bottom of the spindle receives the T-tube G E F, the 

 joint being ground so as to admit of rotation of the spindle 

 around the tube. Air charged with nuclei is conveyed 

 through this tube, entering at F, from an aspirating train 

 presently to be described. 



To obviate the danger of steam entering the tube E F and 

 quenching the " duster," a hollow nozzle, D, is ground into 

 the top of the spindle and removable at pleasure. This 

 introduces the nuclei at about one centim. above the annular 

 opening in the jet where the pressure-excess has practically 

 vanished. The nozzle does not otherwise interfere (tests 

 made) with the action. Should water enter the tube E, it 

 may usually be removed by opening the stopper G. Very 

 little difficulty is thus occasioned from this cause. 



The colour-tube is now modified as shown at C (fig. 2), the 

 jet, J, playing directly into the open bottom of the tube, and 

 as this is telescoped (not shown) the lower section may be 

 raised to facilitate access to the jet. The mirror which throws 

 up daylight is shown at m, n being the observation window 

 cleaned with caustic potash applied with a probang through 

 a. The escape steam-pipe is at e. 



The bottom of the spindle is joined by a thin tube*, t, 

 about one millim. in diameter, to the phosphorus " duster," 

 P, wmich here consists of a glass tube about 30 centims. long 

 and 1 centim. in diameter, containing a succession of thin 

 pellets of phosphorus secured between strips of wire gauze 

 and kept at a temperature of 25°-30°. F is a fine screw 

 stopcock, admitting the compressed air of the gasometer 

 train, of which D is the desiccator, U the pressure-gauge, V 

 the volume-flask (capacity, 8 litres) , graduated on the side in 

 litres, and M a large Mariotte flask of copper raised or 

 depressed by the pulley p. It will be seen that on closing 

 the cocks c and d, of V, the water enters the flask V by the 



* This tube will usually be called the " absorption " tube, because a 

 great number of the nuclei are unavoidably lost here. Cf. ' Science/ xi. 

 pp. 201-206, 1900; Am. Journ. Sci., March 1901. 



