C. Barns — Velocity and Structure of the Nucleus. 231 



coronas of different orders, for phosphorus and other nuclei, 

 present in saturated water vapor to the average extent of 10* 

 per cub. cm., the value h = "1 cra./min. was ascertained. This 

 is equivalent to /c = '5 cm./min., in air saturated with water 

 vapor. 



This datum may now be compared with the diffusion veloci- 

 ties of Table II of this chapter, in which fresh phosphorus 

 and other nuclei were used, densely distributed and tested in a 

 variety of vapors, alcoholic, hydrocarbon, etc. The usual 

 values of diffusion velocity lie between /c = -5 cm./min. and 

 •9 cm./min., being thus of the order of the preceding case. 

 Water vapor itself did not admit of measurement. The value 

 estimated from the filamentary advance immediately after the 

 nuclei enter, 80 cm./min., agrees more closely with the case for 

 atmospheric air at the beginning of the paragraph. As stated 

 elsewhere, there is much in the behavior of water which is 

 left unexplained. When the nuclei are first introduced into 

 the mixture of air and saturated water vapor, the air effect 

 does not seem to be negligible. 



Finally the experiments on the evanescence of the nuclei 

 produced by shaking solutions lead to a series of values of k 

 as follows. A few hundred nuclei per cub. cm. were usually 

 present after shaking the solutions, and less than 50 (usually) 

 after shaking pure water. 



For the saline solutions of 1-3 per cent, of '01 per cent and 

 of '0001 per cent, respectively, k = '25, '1:0, and 10. For pure 

 water k = 2o or even 50. 



For aqueous solutions of solid neutral organic solutes of 1-3 

 per cent, and '01 per cent, /c = -S, and 3, respectively. The 

 acid organic solutes like tartaric acid seem to behave quite 

 differently. The solutions of this body of 2 per cent, '02 per 

 cent and -0002 per cent, showed diffusion velocities of /c = -1, 

 •1, and 1*0, respectively, thus evidencing uniformly greater 

 persistence of nucleation than even the saline bodies. 



For neutral liquid organic solutes in aqueous solution of 1-3 

 per cent and '01 per cent /c = 6 and 12. Nuclei from these 

 bodies are thus very fleeting. 



Finally for hydrocarbon solution of solid hydrocarbons of 

 1-3 per cent, k = -10 or -20, not differing much in persistence, 

 etc., from the salt solutions. 



The total range found for the diffusion velocity of nuclei 

 produced by shaking solutions of less than 3 per cent is tluis 

 from a; = '1 to 50 cm./min., increasing with the degree of 

 dilution of the solution, the largest value cited (pure water) 

 closely approaching the datum for phosphorus nuclei in atmos- 

 pheric air, /c = 90 cm./min. 



These variations of the velocity of the nuclei produced by 



