198 



SCIENCE 



[N. S. Vol. LII. No. 1339 



the research laboratories of the American 

 Telephone &. Telegraph Company and the 

 Western Electric Company, has accepted the 

 position of head of the physics department at 

 Union College and will cooperate with the 

 research laboratories of the General Electric 

 Company in certain research work. 



Professor James T. Rood, of the Univer- 

 sity of Ulinois, has been appointed professor of 

 electrical engineering at the University of 

 Wisconsin. Professor Eood was graduated 

 from the Worcester Polytechnic Institute in 

 1898 and obtained the degree of doctor of 

 philosophy at Clark Institute in 1906. He 

 taught nine years at Lafayette College and 

 has since been two years on the Illinois 

 faculty. 



Ered C. Werkenthin, associate professor of 

 botany in New Hampshire College, has been 

 elected to an instructorship in botany in Iowa 

 State College. 



Dr. Gr. R. BiSBY, formerly of the University 

 of Minnesota, has accepted the position of 

 professor of plant pathology at the Manitoba 

 Agricultural College, Winnipeg, Canada. 



Professor J. T. Wilson has been elected 

 dean of the faculty of medicine in the Uni- 

 versity of Sydney in succession to the late 

 Sir Thomas Anderson Stuart. 



DISCUSSION AND CORRESPONDENCE 



METHODS USED IN THE STUDY OF SOIL 

 ALKALI 



In Science of February 6, 1920, Mr. F. B. 

 Headley, of Fallon, Nevada, took occasion to 

 call attention to imperfections in methods of 

 studying soil alkali used by the Utah Station 

 and some other institutions. His criticism 

 seems to center around two ideas: (1) that 

 we consider that salts added to the soil rep- 

 resent the true concentration of the soil 

 solution; (2) that we did not analyze soils to 

 which salts had been added and that we were 

 therefore entirely ignorant of the amount of 

 alkali the soil contained. 



Answering these in order, I may say that 



in Utah we have never considered salts added 

 to the soil to be anything but salts added. 

 Workers in soil science are fully aware of the 

 fact that when such salts as carbonates are 

 added to the soil they immediately undergo 

 transformations that are not well understood. 

 'No one, so far as I know, would undertake 

 to tell just what the soil solution as it affects 

 plants really is. It is somewhat like trying 

 to tell the composition of living protoplasm. 

 As soon as an attempt is made to analyze 

 the protoplasm, it is killed and its composi- 

 tion is probably changed. Numerous meth- 

 ods for arriving at the concentration of the 

 soil solution have been suggested. These in- 

 clude (1) direct chemical analysis of leach- 

 ings of the soil, (2) subjecting the soil to 

 high centrifugal force in an attempt to throw 

 off some of the real soil solution, (3) placing 

 the moist soil under very heavy pressure to 

 press out some of the solution, (4) attempt- 

 ing to obtain the osmotic pressure of the soil, 

 (5) obtaining the conductivity of the soil to a 

 current of electricity, (6) determining the 

 concentration of salts by the lowering of the 

 freezing- point, and (7) getting the vapor 

 pressure of the soil in order to determine 

 the concentration of the soil solution. 



None of these methods has been entirely 

 satisfactory, but each one has been useful in 

 connection with certain studies. I think it 

 can be said therefore that at present we have 

 no means of measuring the exact concentra- 

 tion of the soil solution as it affects plants. 

 Neither the amoimt of salt added to the soil 

 nor the amount recovered by chemical 

 analyses represents the true value, and in 

 making any interpretation it is necessary to 

 state specifically in each case whether refer- 

 ence is made to " salts added " or " salts ex- 

 tracted." At the Utah Station we have been 

 very careful to say which of these we referred 

 to in every case. 



In a recent publication (Utah Station 

 Bulletin No. 170) we have taken occasion to 

 show the relation of " salts added " to " salts 

 recovered" by extraction using various quan- 

 tities of water and stirring for different 

 lengths of time, by the freezing point method. 



