28 



KXPERIMENTS WlXn IONIZED AIR. 



TABLE 6— COLORS COMPARKD LN RELATION TO DUST NEEDED, lU' SUMNLV- 



TION OR RY DIMERENCE. 



Tlie difficulty witli tliis method, though beautiful in principal, is the large 

 error introduced at each color discrimination. Thus iu an e(piation with three 

 tubes there will be four terms and four corresponding discrepancies for the colors. 

 I did not, therefore, pursue the method further, merely noting its general 

 agreement with the data of the chart, figure 3. 



10. MoJified color tube. — The color tube, as above used, has two grave 

 disadvantages, inasmuch as in the first place the quantity of steam issuing at 

 a given pressure cannot be easily varied, and in the second place, the manner in 

 which the dust is brought into the Jet is not easily understood. One is not sure 

 that the whole of the dust is actually brought to bear in producing condensation 

 when the charged air comes in contact with the jet from without, as at CC, 

 figure 1. Again the colors of higher order are best seen at relatively low 

 temperatiues and pressures, but I'equire a large volume of steam if they are not 

 to be too faint for recognition. First order colors require almost the opposite 

 conditions, etc. Many of these desiderata are met in the foUowinsr device, fisrure 

 7, for axial intlu.v, wliicli has the further advantage of making the jet more easily 

 accessible; for the saturation of colors, even of higher orders, is now such that 

 the lower window and Literal intlux pipe of the color tube, figure 1, Chapter I, 

 may be dispensed with. 



The jet, figure 7, is annidar in patern, the l)ullet-sha[ied body, A, being 

 a hollow conoid about 5 cm. long and about .9 cm. in diameter internally, provided 

 witli a lateral tubulnre, 7, for the influx of steam from the steam box. The 

 body being open above and below receives the hollow spindle BC axially, 



