STEAM JET. 



IOI 



must be relieved to reduce the excess before the field clears again, in 

 greater measure as the temperature is lower, until at 9 steam issuing 

 at ordinary pressure (without appreciable pressure above one atmos- 

 phere) condenses spontaneously. 



The increments of supersaturation below 40 are in fact considerable. 

 Thus, if the saturation at 40 be taken as the standard, these excesses 

 would be roughly as shown in table 40. 



Table 40. Estimated supersaturations. 



Temperature. . . 

 Supersaturation 

 Relation 



io~ 6 g/cm 3 



These values are to be added to whatever supersaturation preexists 

 at 40 , seeing that the escaping steam is always suddenly cooled down 

 from a temperature much above ioo. In fact, the following data 

 (table 41) may be adduced from the diagram, if t t be the temperature of 

 the steam before, t 2 the temperature after, p t and p 2 the densities of 

 the steam. 



Table 41. Estimated supersaturations. 



L 



Pi 



*, 



Pi 



S=pjp.,. 



io~ 9 g/cm 3 

 io _6 g/ cm 3 



Nothing more than exhibition of the order of values is intended; 

 but it will readily be seen that in comparison with Wilson's data (S = 4.3 

 for rain-like, S = 7-6 for cloud-like condensation, and 5 = 9.9 f r the 

 sensitive tint), the supersaturations here are enormous, and that the 

 condensations must take place on something approaching the molecular 

 groups of the system, water steam air. 



It is therefore scarcely necessary to remark that the data are superior 

 limits, particularly inasmuch as the influx temperature at C, fig. 50, and 

 not the efflux B, were taken. But as the influx of air is swifter as the 

 the steam pressure increases, the difference between these temperatures 

 is not large. The escaping steam is always cool to the hand. 



It follows that the color data bear at once on the structure of dust-free 

 air. The occurrence of definite loci for r, y, g, b, v, the fact that any 

 color can be retained indefinitely, if (cat. par.) the pressure-temperature 



