464 



SCIENCE 



[N. S. Vol. XL. No. 1031 



especially by Perrin's work, so that much 

 of the basis of this difficulty may be fairly 

 considered as now removed. 



Quite analogous to the reduction from 

 the normal of the moisture held by a semi- 

 permeable medium brought about by the 

 addition of salt to the water, is the reduc- 

 tion in the vapor pressure arising from the 

 presence of a salt in the water. The vapor 

 pressure is likewise increased by the appli- 

 cation of hydrostatic pressure, which may 

 be effected by means of an inert gas. In 

 both cases the hydrostatic pressure which 

 must be applied to bring back to normality 

 is equal to that which the added salt would 

 exert if it were in the state of vapor or, in 

 other words, the osmotic pressure. 



The two cases are really very similar. 

 In both there is equal molecular transfer 

 backwards and forwards across the bound- 

 ing surface. In the one a transfer from 

 that solution to the semi-permeable medium 

 and back from it into the solution. In the 

 other a transfer from the solution into the 

 superambient vapor and back from it into 

 the solution. 



The processes are very similar, namely, 

 equal molecular transfer to and fro across 

 the respective surfaces of separation. 



Thus we may in the case of osmotic equi- 

 librium attribute the phenomenon with 

 Callender to evaporation, but not evapo- 

 ration in its restricted sense, from a free 

 surface of liquid, but as we have seen from 

 a saturated colloidal surface into the so- 

 lution. This process might perhaps be bet- 

 ter referred to as molecular emigration, 

 the term migration being already a fa- 

 miliar one in connection with liquid phe- 

 nomena. F. T. Teouton 



TSE SPIRIT OF A VNIVEBSITY 



A DECADE ago in the United States of 

 America, in a university rated among the 

 first in numbers of students, the professor 



of astronomy was summoned before the 

 president and the governing board and 

 asked whether he believed the nebular hy- 

 pothesis which he discussed in a text-book 

 issued under his name. An answer in the 

 affirmative was promised to cost him his 

 teaching position. He answered in the 

 negative, and to prove his sincerity as- 

 sented to calling in his books and having 

 them burned in public. A less number of 

 years ago a university president whom we 

 to-day honor as a first citizen found it well, 

 or shall we say necessary, to step out of his 

 chosen field of work because he held the 

 minority view among his associates that the 

 word democracy does not mean a political 

 party only. Some months ago a professor 

 of philosophy, teaching its principles as 

 he saw them and under a freedom appar- 

 ently guaranteed him by charter, alleges 

 his resignation is requested because such 

 teaching in the mind of his president is in- 

 compatible with the doctrinal views of an 

 avowedly religious organization operating 

 in some state or states of our Union. 



Again, the members of a faculty wake to 

 their accustomed labors and over the coffee 

 and in the newspaper receive first word 

 that their places have over night been de- 

 clared vacant; a university president de- 

 mands that his faculty vote Yes or No as 

 an expression of their confidence in him; 

 a faculty member backed by brains and 

 fearlessness rises to condemn most of those 

 time-sanctified institutions of boards of 

 control and university presidents. 



It is well to emphasize that these illus- 

 trations do not represent hand-picked rari- 

 ties, but are typical of a class of problems 

 which in greater or less degree arise peri- 

 odically to clog the machinery of university 

 education. Neither can it be said that a 

 correct solution is not usually found for 

 them. The only question of importance is 

 why the delay in so doing and why so much 



