132 ON THE TIMBER SUPPLY OF AUSTRALIA. 



Humboldt, visiting the town, ascribed the gradual diminution of 

 the water to the extensive clearings of the forests. Twenty-five 

 years later the waters of the lake had gradually risen again, agri- 

 cultural operations having almost ceased, and the forest regained 

 possession of the soil. "Whatever may be the direct effects of trees 

 on the rainfall, there is no doubt that the actual temperature of 

 the country becomes considerably higher by the destruction of its 

 forests. Trees attract moisture, and retain it ; their roots retard 

 too rapid drainage, their presence benefits springs, their shade 

 checks evaporation ; and we shall have heavier dew in the neigh- 

 bourhood of forests. Sir George Strickland Kingston says, in his 

 valuable "Notes on the Rainfall of Adelaide, Melbourne, and 

 Sydney," printed in Parliamentary Paper No. 10, of 1875 : " Dur- 

 ing the first four months of the year want of moisture in the 

 atmosphere, accompanied by intense heat, putting a stop to vege- 

 tation, and baking the surface of the ground, has a somewhat 

 similar effect, in so far as agricultural pursuits are concerned, to 

 that produced by the wet and frosts of the winters of England. 

 The benefit of the rainfall depends not so much on the quantity 

 during a given month as on the rapidity or otherwise of its fall, 

 as well as the season of the year." After stating that during the 

 first four months of the year nothing under an inch of rain at one 

 fall is of much value to renew the exhausted energy of vegetation, 

 he remarks that from the end of April to September the quantity 

 of rain during the twenty-four hours is of little importance as com- 

 pared with the frequency of its occurrence, keeping the ground 

 moist, and provided that the average of the monthly falls are 

 fairly kept up, the ground is more benefited by the occurrence of 

 numerous rainy days than by a great fall in any one day. As an 

 instance he mentions the year 1860, where the rainfall was much 

 below the average, yet the harvest was in excess of the average 

 yield of the four years 1855 to 1858, in which the rainfall was 

 considerably above the average. But the rains were gentle, con- 

 tinuing for several hours, soaking into the ground, and being fol- 

 lowed by many days of cloudy weather, little or no evaporation 

 took place, and the crops derived the fullest possible benefit from 

 the limited quantity of rain." This is unquestionably true ; and 

 I believe that tree plantations will add to the number of showery 

 days and the general humidity of the climate. The former and pre- 

 sent climate of St Croix is a case in point. As long as trees were 

 everywhere abundant on this island rains were profuse and fre- 



