30IL8 FERTILIZERS. 535 



retain moisture in equilibrium with the atmosphere a- influenced l>> proportion and 

 character of organic material, relative proportions of mineral particles of differenl 

 Bizes, chemical and physical nature of mineral constituents, and temperature and 

 humidity of the atmosphere. The studies were made with fine earth passing a sieve 

 w it h meshes 3 nun. in diameter. 



A mathematical exposition is given of the bearing of the analytical data on the firsl 

 three factors named, and two series of experiments are reported. In the firsl of these 

 "a number of small weighing bottles were prepared, containing respectively a gram 

 each of five different soils and of their Bix fractions. These were pul under a bell- 

 jar, together with a dish which contained during mosl of the experiments a solution 

 of calcium chlorid of which the concentration was determined when the bottles were 

 removed for weighing; at the conclusion of the series the dish was filled with granu- 

 lar calcium chlorid in order to obtain the weight of the samples in equilibrium with 

 a dry atmosphere. The water lost at 95° and the loss on ignition were also found, 

 but all results air calculated t,, tin- weighl of the material dried in this manner in 

 the cold." 



In order to overcome irregularities in individual figures observed in the first series, 

 "the second series of experiments was extended over a greater number of observa- 

 tions, and more duplicates were used. The standard weights attained in a cold, dry 

 atmosphere were determined eight times, five times over granular calcium chlorid, 

 and three times over fused caustic potash, and the results obtained were in most 

 cases in satisfactory agreement." 



The more important conclusions reached are that "the organic substance not only 

 has a powerful direct influence in attracting moisture, but it also acts indirectly, so 

 that t lie joint effect of the organic snhstan.ee and the surface of the mineral particles is 

 not merely an additive property. The organic material probably serves to keep the 

 finer grades of mineral matter apart and free to exercise surface attraction far more 

 effectually than the coarser mineral particles are able to do. It appears that the 

 organic substance in different fractions ha- not always the same hygroscopic power. 

 . . . Mineral particle- of the same size in different soils have not identical 

 hygroscopic power. . . . The finest grade particle-, especially the clay fraction, 

 show specially high attraction for water in atmospheres of extreme moistness. . . . 



•• It follows from the foregoing that the attraction of mineral particles for moisture 

 can not he strictly expressed as simply proportional to their surface, and it is readily 

 -een that many apparent irregularities in the tables are due to the causes [noted 

 above]. But within certain limits as to moisture in the atmosphere, and in spite of 

 the disturbing influence of other factors such as the varying attraction of the organic 

 material, its indirect action, and the special hygroscopic action of iron oxid and per- 

 haps other soluble minerals, there is a regularity in what is here called the moisture 

 multiple, so that it tends to assume a value inversely proportional to the diameter 

 raised to the two-thirds power. . . . 



"■ It appears as if the use of the two-thirds power ratio was most suitable for the 

 majority of cases, but in the case of the finest particles in a very moist atmosphere 

 the increase in moisture gained proceeds at a far higher rate." 



The moisture of the soil in the climate of Tunis, F. I'.n.i i and Tournieroux 

 [Bui Dir. Agr. et Com. [Tunis], 9 {1905), No. SS, pp. ?86 SOS, fig. 1, chart n.—\ 

 large number of determinations of moisture in cultivated and uncultivated .-oil and 

 during different seasons i rainy and dry i of the year ended June 30, L904, are sum- 

 marized. 



[n the soils studied the moisture varied from 1 to 20 per cent, [n soil which had 



been dug up to a depth of 0. If) meter I 5.91 in. i the moisture varied from 8 t<> 20 pet- 

 cent, in soil which had been cultivated after removal of the crop of wheat the varia- 

 tion was from 5 to 15 percent, and in uncultivated soil 5 to 18 per cent. The improve- 

 ment of the capacity of the soil for storing and retaining water by digging was quite 



