70 EFFECTS OF FORESTS ON HUMIDITT. 



other. In the case supposed, the affinity for moisture will be found 

 to be proportionate to the different results ; but it may be modified 

 by the proportions of clay, if in either this be greatly in excess — and 

 this also can easily be determined. 



If the two parcels of soil be next drenched with hot water, and this 

 poured off when discoloured with the muddy matter suspended in it, 

 and the process be repeated until the water comes off limpid, upon their 

 being again desiccated in an oven, as before, and weighed, the loss 

 they have sustained in weight will indicate the quantity of clay which 

 was in their composition, together with free soluble salts, the quantity 

 of which may be little or may be much. Thus will have been re- 

 moved all the materials manifesting a marked affinity for atmospheric 

 moisture; and in few cases, if any, the results greatly modify the con- 

 clusion arrived at by the removal of the humus and its constituents. 



I prescribe not these proceedings as certain to give precise results, 

 in absolute accordance with the actual constitution of the soils made 

 the subject of expei'iment, but as rough and ready experiments which 

 may be made by the inexperienced, the results of which will indicate, 

 and to some extent measure, the property of forest soil not only to 

 retain moisture, but to attract moisture from the atmosphere in a 

 superior degree to that in which such property is possessed by the 

 gravelly and sandy soil taken from the highway. 



Should any one desire more accurate results, the following course 

 of procedure may be followed : — 



1. Ascertain the quantity of moisture in the apparently dry soil 

 by the mode of desiccation described, weighing the soil before and 

 after the operation. 



2. Ascertain the affinity for moisture by lengthened exposure of 

 the desiccated soil to the air anywhere, and subsequently weighing 

 it to learn what it has gained. 



3. Ascertain the quantity of organic matter in the soil by heating it 

 to incandescence as directed, but doing this in a plantinum crucible, 

 previou&ly desiccating it as before, and weighing it before and after 

 this third operation. 



4. Drench it with spirit of salt, muriatic acid, or hydrochloric acid, 

 as it is now generally designated, adding soft water, and continuing 

 the operation till all effervescence has ceased. Drench it then with 

 water ; let it settle ; pour ofi" the water when limpid ; desiccate as at 

 first, and weigh : and the loss of weight will then indicate the 

 quantity of lime which was in the soil. 



