64 



THB DIFFUSION OF GASES THROUGH 



are inadmissible, that diffusion decreases with the length of column at a 

 retarded rate; or that the normal volume of gas diffusing per second 

 through a column, cat. par., is not directly dependent upon the pressure 

 gradient, but decreases more rapidly than the gradient. For long, slender 

 swimmers, /=ii to 12 cm., k is so much reduced as to suggest that for 

 greater lengths of column it would practically vanish. Such a behavior 

 was quite puzzling. The only method of interpreting it seemed to consist 

 in continuing the observations in table 20, while the diver in table 19 was 

 cut down to half its length for correlative observation. 



The apparatus E, after the long swimmer had been cut down to the small 

 length, showed the results recorded in table 20 and fig. 19 c. 



Table 20. — Air-air through water. Vessel £. Small swimmer. il/= 12.4716 grams; 

 p^=2.466; C=44.8o; float, 2r = 3.oo cm.; vessel, 2r=:4.7 cm. 



A line drawn through the observations as a w^hole is equivalent to the 

 following rate : 



'^0 = 0.0232 c.c./'day or 10^^ = 0.64 



This, though small, is a closer approach to the normal value for air found 

 in Chapter II. The result, however, might nevertheless give credence to 

 the occurrence of a length effect, since it may imply that diffusion varies 

 with the length of diver and column. This improbable and disconcerting 

 eventuality is dispelled by the final data of table 1 9 for the long diver after 

 the time interval of observation had been adequately increased. It follows, 

 therefore, that these long divers merely accentuate the discrepancy due to 

 the thermal changes of solution; for the results obtained with the long 

 swimmer are (fig. 19B): 



?o = 0.0082 c.c./day and io^*^k = o.78 



which agree admirably with the results of Chapter II. (See table 21.) 

 The length effect is thus, fortunately, illusory. 



