PIIY£,:CAL CHARACTEUS OF THE SOIL. IGl 



ing roots have in whicli to expand themselves, and the 

 more abundantly are they able to present their absorbent 

 Burfaces to the supplies which the soil contains. The fine- 

 ness of the particles may, however, be excessive. They 

 may fit each otlier so closely as to interfere with the 

 growth of the roots, or at least with the sprouting of the 

 seed. The soil may be too compact. 



It will presently a})pear that other very important prop- 

 erties of the soil are more or less related to its state of 

 mechanical division. 



§ 3. 

 ABSORPTION OF VAPOR OF WATER BY THE SOIL. 



The soil has a power of withdrawing vapor of water 

 from the air and condensing the same in its pores. It is. 

 in other words, hygroscopic. 



This i^roperty of a soil i-; of the utmost agricultural im- 

 portance, because, 1st, it is connected with the permanent 

 moisture which is necessary to vegetable existence ; and, 

 2d, since the absorption of water-vapor to some degree 

 determines the absorption of other vapors and gases. 



In the following table we have the results of a series 

 of expeiiments carried out by Schablor, for the purpose 

 of determining the absorptive power of different kinds of 

 earths and soils for vapor of water. 



The column of figures gives in thousandths the (quantity 

 of hygroscopic moisture absorbed in twenty-four liours by 

 the previously dried soil from air confined over water, 

 and hence nearly saturated with vaj)or. 



Quartz suud, course 



Gypsum 1 



Lime sand 8 



Ploii.^h laud 2:^ 



Claj' soil, (60 per cent clay) 28 



Slaty marl ;?3 



Loam , 35 



