EVAPORATION FROM THE SOIL. 135 



face. attraction of the particles of the soil for water. The 

 finer the particles of the soil, the greater quantity of water 

 is absorbed, because the total surface is greater. The nat- 

 ural result of this is, that the slower is the evaporation from, 

 the soil, because the natural affinity of the surfaces for mois- 

 ture being greater it is proportionately harder to overcome 

 it by evaporation. The following table gives the results 

 reached by Schubler in experiments in this direction. 

 In the first column the figures are nearly a repetition 

 of those given in the last preceding table, but they 

 are here placed in juxta-position with the second column, 

 which shows the quantity of water which was evaporated 

 in 4 hours when the samples of the soil w r ere spread over 

 equal surfaces and exposed to the same conditions. 



Per cetd. Per cent, of 



of water water evaporated 



aosorbed. in 4 hours. 



Quartz sand 25 88.4 



Limestone sand 29 75.9 



Clay with 40 per cent, sand 40 52. 



Loam 51 45.7 



Common arable land 52 32. 



Heavy clay 20 per cent, sand 61 34.6 



Powdered carbonate of lime 85 28. 



Garden soil 89 24.3 



Peat decayed 181 25.5 



This resistence to evaporation is not only due to the ad- 

 hesion of the water to the surfaces of the particles of the soil, 

 but is due to capillary attraction. If a capillary tube, that 

 is one having a very small diameter, is dipped into water a 

 portion of its length ; the water wdthin the tube rises con- 

 siderably above the level of that without it. This is due to 

 what is known as capillary attraction. If a piece of woolen 

 cloth is hung over the edge of a pail half full of water, so 

 that one end is in the water, the water will rise through the fi- 

 bers of the cloth ; these forming capillary tubes ; and will flow 

 over the edge of the pail until the pail is emptied. If two 

 sheets of glass are placed in a vessel of colored water, and 

 the two edges are brought into contact at one side 

 and separated a small space at the other side, the col- 

 ored water will be seen to rise between the plates and 



