EFFICIENCY OF FOG CHAMBER. 



35 



that the nucleation of the exhausted fog chamber is specified. Otherwise 

 it would be necessary to multiply by the ratio of volumes after and before 

 exhaustion. 



Diagrams of the apparatus used have already been given in Chapter 

 II (figs, i to 4), and further examples will be shown of the details of the 

 more perfected forms below (figs. 26, 34, 64). In those paragraphs, 

 moreover, I will treat the corrections to be applied (which are much 

 larger than were anticipated) in order to pass from the observed appar- 

 ent dp to the true values. These must be computed from the volume 

 ratio of the two chambers and their respective initial and their final 

 isothermal pressures when in communication. 



36. Examples of data for l=inch connecting pipes. These were about 

 18 inches or more in length and the stopcock inserted was i^ inches in 

 bore, as specified in the preceding chapter. The plug was as usual 

 floated in paraffin oil, absolutely preventing the influx of atmospheric 

 air, though some leakage (which is generally harmless) from the fog 

 chamber to the vacuum chamber could not be prevented. The fog 

 chamber in these exhaustions had a rather larger charge of water than 

 usual, a circumstance to which the higher fog limits may possibly be 

 due, since these vary with the volume ratio. 



Table 12. Pipes 1 inch, cock 1$ inches. Non-energized 

 dust-free air. October 24. 



The results are to be shown below (fig. 22, p. 37) in comparison with 

 the later values and may be passed over here. 



37. Data for pipes 1.5 inches in diameter. Fog chamber and vacuum 

 chamber were now connected by brass gas pipes i\ inches in diameter 

 and 2 feet long, and the plug stopcock interposed was 2 inches in bore. 

 In the case of table 1 3 the disposition of apparatus was such as to require 

 the length of piping specified with an elbow. The results are given in the 

 usual way and show a distinct gain in efficiency over the earlier set in 

 table 13, proving that greater width of pipe is still an advantage. 



