January 3, 1902.] 



SCIENCE. 



35 



escapes out into tlie gravitational spaces by 

 diffusion. 



Wlien the rain ceases the gravitational 

 spaces drain of water, carrying off relatively 

 a small part of the soluble matter, and the 

 evaporation from the surface causes the up- 

 ward movement to commence, but this move- 

 ment is entirely capillary and the whole film 

 around the soil grains moves, and as it moves 

 so does all of the salt except possibly that por- 

 tion absorbed, and there is evidence which leads 

 one to believe that the absorbed salt moves 

 also, but rather more slowly than the film; 

 that is, the absorbed salt shows a tendency to 

 lag behind. 



Therefore, it will be seen that the rains do 

 not move the salt as far down as they pene- 

 trate but leave the most of it near the surface 

 of the soil or at least so close to the surface 

 that capillary movements will again -accumu- 

 late at the surface as soon as the dry season 

 occurs. 



This explanation of the movement of soluble 

 salts within a soil finds application in a num- 

 ber of ways. In the arid regions, where the 

 soluble salts are more abundant than in the 

 humid climate, and where the movements of 

 these salts, if not understood and controlled, 

 ofttimes result in the accumulation of soluble 

 matter this explanation of the difference in the 

 rate of downward movement, compared with 

 the upward movement, goes far to explain 

 some points which were heretofore but imper- 

 fectly understood. For example, it has always 

 been difficult for the writer to understand why 

 alkali salts should continue to accumulate at 

 the surface of the ground in spite of the re- 

 peated irrigations, and the maxim laid down 

 by agriculturists in that region that 'aU^ali 

 goes with the water.' In one district of es- 

 pecial notoriety in California the water table 

 was thirty years ago about sixty feet below the 

 surface of the ground and there were no indi- 

 cations of alkali. Irrigation was commenced 

 and continued large and excessive quantities 

 were used. All of the time the water table was 

 steadily rising, showing unquestionably that 

 more water went downward through the soil 

 than came up for evaporation, and yet in spite 

 of this accumulative downward movement of 



the water the aUvali salts, which, so far as can 

 be gathered from adjacent unirrigated areas, 

 was within the surface twenty feet of the soil, 

 have been steadily creeping upward and at the 

 present time fully ten per cent, of the area is 

 suffering from an excess of allcali salts. 



It is plain that if we desire to send the salts 

 downward the easiest way to do it is to make 

 the downward movement, as far as possible, 

 capillary instead of gravitational. One way of 

 doing this is to break up the soil gravitational 

 spaces by deep cultivation and subsequent 

 firming by flooding. Such has been found very 

 effective in certain areas of Arizona. Another 

 way is to flood the soil with frequent shallow 

 irrigations. In this way a slow downward cap- 

 illary current is kept up. Half a dozen flood- 

 ings with one inch of water each will be found 

 to carry downward much more salt than one 

 flooding of six inches. 



Another lesson taught, one well known for 

 many years, is that if the subsurface water is 

 alkaline it must not be allowed to rise so close 

 to the surface that continuous upward cap- 

 illary movement is possible; else the alkali 

 will accumulate in the soil, to its detriment. 



Thos. H. Means. 

 Bureau of Soils, 



Washington, D. C. 

 CHEMISTRY IN THE CALIFORNIA SCHOOLS. 



The chemistry teachers of the Pacific coast 

 have organized an association to encourage the 

 teaching of chemistry, to harmonize methods, 

 to become acquainted with each other and with 

 the needs of the country and the conditions af- 

 fecting their profession ; and, generally, for all 

 those purposes for which association is good. 

 The organization was effected last August, 

 during the Summer School session of the 

 University of California, at which many 

 teachers from California and from the neigh- 

 boring States were present. The headquarters 

 of the organization are at Berkeley, which, as 

 it is the educational center of the western part 

 of the country, is the natural location for such 

 a purpose. Two members of the faculty of the 

 University of California, one in the depart- 

 ment of chemistry and one in the department 

 of physics, were among the organizers. 



The need for such an organization is shown 



