150 HOW CROPS PEED. 



pass it. The apparatus being joined together, and the 

 cock opened, the soil in 1 is agitated by tlie stream of wa- 

 ter flowing through, aud the finer portions are carried ovef 

 into 2, 3) 4; and 5. As a given amount of water requires 

 eight times hunger to pass through 2 than 1, its velocity 

 of motion and buoyant power in the neck of 3 are corre- 

 spondingly less. After the requisite amount of water has 

 run from A, the cock is closed, the whole left to rest sev- 

 eral hours, when the contents of the vessels are separately 

 rinsed out into porcelain dishes, dried and weighed.* 



The contents of the several vessels are designated as 

 follows :f 



1. Gravel, fragments of rock. 



2. Coarse sand. 



3. Fine sand. 



4. Finest or dust sand. 



5. Clayey substance or impalpable matter. 



In most inferior soils the gravel, the coarse sand, and 

 the Jine sand, are angular fragments of quartz, feldspar, 

 amphibole, pyroxene, and mica, or of rocks consisting of 

 these minerals. It is only these harder and less easily 

 decomposable minerals that can resist the pulverizing 

 agencies through which a large share of our soils have ' 

 passed. In the more fertile soils, formed from sedimen- 

 tary limestones and slates, the fragments of these strati- 

 fied rocks occur as flat pebbles and rounded grains. 



The finest or dust-sand, when viewed under the micro- 

 scope, is found to be the same rocks in a higher state of 

 pulverization. 



* See, also, Wolff's " Ardeitung zur Untermchung landiDirtlischaftlich-wichtiger 

 Stofe," 1867, p. 5. 



t These names, applied by Wolff to the results of washin;; 'he sedentary soils 

 of Wijrtemberg, do not always well apply to other soils. Thus Grouveu, {3ter Salz- 

 munder Berkht, p. 32), operating on the alluvial soils of North Gennany, desig- 

 nated the contents of the 4tli funnel as "clay and loam," and those of the 5th 

 vessel as " light clay and humus." Again, Schiine found {Bulletin, etc., de Moscou, 

 p. 402) by treatment of a certain soil in Nobel's apparatus. 45 per cent of "coarse 

 sand " remaining in the 2d funnel. The particles of this were for the most part 

 emalkr tliau 1-lOtk millimeter (l-350ih inch), which certainly is not coarse sand i 



