Causes of dryer Climate : Atmometers. 



19 



served a noticeable increase in the dryness of the climate since set- 

 tlement first began. This may in part be attributed to the cleariug 

 away of the belts tf native timber along the streams. The roots 

 of these trees formerly kept the channel at a higher level, and in 

 some cases formed extensive swamps. The beds of these streams 

 are now lower, and they drain oif the water to a greater depth. 

 The effect is shown in the failure of water in the wells, and in the 

 more frequent occurrence of drouth, to the injury of agriculture. 



78. There is nothing that would more effectually check this tend- 

 ency to deepening of channels than the planting of willows along 

 the sides, and it might eventually in some degree restore what has 

 been lost by raising them to a higher level. 



79. The rate of evaporation from the surface of water and from 

 soils is found to be much more in the open fields than in woodlands, 

 and the difference is greater in summer than in winter. 



80. Instruments for measuring the evaporation are sometimes 

 called " atmometers,'' and they are of various forms. We here pre- 

 sent a section of one in- 

 vented by Professor La- 

 ment, of the Munich Ob- 

 servatory. It consists of a 

 basin of water, /, g, with a 

 narrow opening at A, com- 

 municating with a reservoir 

 in an adjacent cylinder. 

 Into the latter a plunger 

 may be pressed down or 

 raised by the screw, S. It 

 works through an air-tight 

 collar, a, d, and by this 

 means the water, by press- 

 ure or suction, may be ad- 

 justed in the open basin. 

 When left for observation, 

 the water is drawn down 

 till it is just visible at A, 

 and the scale, s, s, is ad- 

 justed to a zero point at h. 

 It is then forced up till 



Lament's Atmometer. 



