AGRICULTURE AND RURAL ECONOMY. 355 



455,950 tons of suspended matters and 518,900 tons of dis- 

 solved matters making, in all, 974,850 tons. This includes 

 some 117,000 tons of lime, 23,440 tons of magnesia, 45,430 

 tons of potash, 33,000 tonsof soda ; 21,100 tons of chloride of 

 sodium, 38,080 tons of sulphuric acid, and 1250 tons of phos- 

 phoric acid (Dingl. Polyt. Journal, ccxxiii., 328). 



Soil -Absorption. 



One of the most important factors of the fertility of soils is 

 their faculty of absorbing the ingredients of plant-food from 

 their solutions, and retaining them for the use of plants. In 

 a new work by Detmer on soils ("Die Naturwissenschaft- 

 lichen Grundlagen der Bodenkunde"), 60 pages, and in ThiePs 

 " Landwirthschaftliches Conversations -Lexikon" (Agricul- 

 tural Encyclopaedia) now being issued, 12 pages, are devoted 

 to the discussion of this subject. Detmer gives conclusions 

 essentially as follows : 



1. Ammonia, potash, lime, magnesia, sulphuric acid, silica, 

 and phosphoric acid may be absorbed by soils. Nitric acid 

 and chlorine are not absorbed to notable extent. 



2. When these substances are supplied in the free state to 

 a soil, they enter into combination with its ingredients. When 

 a base is absorbed by the soil, from a salt in solution, an equiv- 

 alent amount of another base leaves the soil, and goes into the 

 solution. 



3. The soil absorbs a given ingredient of a salt most ener- 

 getically when the other ingredients of the salt are at the 

 same time recombined. 



4. From very dilute solutions nothing is absorbed. 



5. The time of contact between soil and solution does not 

 essentially affect the amount of absorption. 



6. The absorption is increased by heat, and is peculiarly 

 affected by the amount of soil and the amount and concen- 

 tration of the solution. Nos. 4 and 6 refer more especially 

 to the observations made in laboratory experiments. 



Heiden, the author of the article on Absorption in the 

 Encyclopaedia referred to, who has himself made a good 

 many experiments upon the subject, arrives at conclu- 

 sions not widely different from those of Detmer. He 

 shows, however, that the absorption of sulphuric acid is 

 very slight. 



