VERMONT AGRICULTURAL, REPORT. 105 



this matter. The wick and the soil, the oil and the water, 

 the flame and the sun's rajs, are similar. As the oil is drawn 

 upwards between the minute crevices of the thread of the 

 wick until it reaches the top, so is water drawn upwards in 

 the soil through its small tubes. If the lamp remains un- 

 lighted the oil is not vaporized and lost ; if it is lit, more oil 

 is pulled upwards to replace that which is consumed, until all 

 is gone. Similarly, if the burning sun rest upon, or scorch- 

 ing winds blow across a soil, its water is sucked out, vapor- 

 ized and lost. 



Now, while this force of capillaritv is of the utmost im- 

 portance to plant growth in that it keeps bringing water and 

 plant food from levels lower than plant roots can readily 

 attain, there are frequently cases when this water is largely 

 vaporized from the surface of the soil and an insufficient sup- 

 ply afforded the plant. Cultivation may be used to control 

 this matter, to lessen the loss by vaporization, to markedly 

 increase the supply available for plant uses. How can these 

 things be? Let us study one of the peculiarities of capillar- 

 ity. The smaller the diameter of the tube, the easier the wa- 

 ter will " flow up hill," the quicker its transfer from lower 

 levels, and the greater the loss. On the contrary, if these 

 tubes be either widened or clogged at the surface, the water 

 can rise to the point where they are widened or obstructed and 

 no further. Prof. Roberts of Cornell has illustrated this point 

 very nicely. A boy at the bottom of a dry stoned well, if the 

 well was narrow enough to permit him to dig his toes and 

 fingers in between the crevices on either side were no boy if 

 he could not readily climb out and escape. If, however, the 

 well widened out near the top or was covered with rubbish, 

 the boy would climb so far and no farther. The shallow cul- 

 tivation of a growing crop repeated every week or ten days, 

 or after small showers, will keep an earth mulch, a fine 

 dust blanket, on the field, and will widen some and clog other 

 capillary tubes and save for plant uses a large proportion of 

 the water which would otherwise be vaporized from the sur- 

 face of the soil. 



This water, now percolating under the influence of rain, 

 now rising by capillarity, keeps the roots bathed in a dilute 

 solution of plant food brought from places they cannot reach. 

 If vaporized, it places this plant food on the surface, or so 

 near it as to be either a detriment, as in the alkali soils of the 

 west, or useless. Crops need vast amounts of water. Exper- 

 iment has shown that for every pound of dry matter the com- 

 mon field crops contain, they need, in order to make their 

 proper growth, from 200 to 500 pounds of water. This may 

 be supplied with relative ease by irrigation. Rains some- 



