THE PREVENTION OF DROUGHT. 163 



" During summer, a mean monthly difference of 

 five and even six degrees is of considerable impor- 

 tance ; and even supposing it to be reduced to half 

 that amount by the time the sap has reached the 

 leaves, it still lowers very perceptibly the tempera- 

 ture of the whole plant. This effect is increased 

 by that evaporation from the leaves which results 

 from the descent of the sap during the day ; so that 

 the hotter the air is, the greater are the resources 

 which the plant finds within itself, and the earth in 

 which it grows, for diminishing the eff"ect of external 

 heat." 



The prevention of drought. Mr. John Sincham, in 

 his work for the use of the engineer, thus enumer- 

 ates the efi"ects of pulverization : " It makes the 

 drains efficient almost immediately and perma- 

 nently. It enables the crop to be planted and 

 harvested much earlier. It is the first and great 

 step towards increasing the depth, and improving 

 the condition of all light, bad soils. It allows the 

 atmosphere to penetrate and circulate freely through 

 the soil, and admits carbonic acid gas and oxygen 

 to the roots of plants, to act upon the deleterious 

 ferruginous compounds and secretions to be found 

 in most soils. It secures also to them benefit from 

 every drop of rain that passes through the atmos- 

 phere." 



