236 J. H. MAIDEN. 



than when the surface was covered with grass. The 

 question of conservation of moisture is many sided and 

 must be considered in all its bearings in order to form just 

 conclusions. 



To say that the regular and permanent flow of the streams 

 is owing to the felling of trees is easy, but to explain the 

 causes is difficult. I have already stated that the natural 

 forest growth retards the flow of the water and hence 

 tempers floods. The continued cutting of trees may cause 

 the flow to be regular under normal (i.e., non-flood) con- 

 ditions. What is the cause? Is it transpiration? I think 

 there is still much room for research on the subject, for 

 some of the statements appear to be absolutely contra- 

 dictory at first sight. 



We have very few data of practical value not only in 

 regard to transpiration but also in regard to absorption. 

 We have many laboratory results, but these inductively 

 applied to a congeries of roots, or a congeries of leaves 

 forming a forest, produce in many cases absurd results. 

 For example, we have results when worked out which show 

 that a gum tree absorbs and transpires incredible quantities 

 of moisture, figures which literally make one's mouth water 

 in this thirsty land. 



Professor Pernow gives a remarkable illustration of the 

 difficulties that surround attempts at quantitative deter- 

 minations of hydrographic investigations of a watershed. 

 For example, the amount of annual discharge of the river 

 Rhone corresponds to a rainfall of 44 inches over the water- 

 shed, while the rainfall records themselves for a certain 

 period give a precipitation of only 27*6 inches. Truly 

 meteorological and kindred data require to be interpreted 

 by experts. Professor Fernow makes the suggestive 

 statement : — 



"The water capital of the earth consists of two parts, the fixed 



