6 TEBE CULTURE IN SOUTH AUSTRALIA. 



To mitigate these floods very considerably there are two courses open 

 to us, viz. : — 1st, by an extended system of arable farming ; and 2nd, by 

 planting large masses of trees. 



First then, as to the benefits to be derived from' more extensive tillage 

 operations. It has been remarked to me that, of late years, not only has 

 the rainfall in the colony been as much as it used to be when larger 

 forests existed in the country than there are in it at the present time,' 

 but that even the floods are not now so extensive as they were. 

 These facts are accounted for thus : — Now that considerable portions of 

 the coimtry have been put under the plough, and the soil become broken 

 up and rendered more porous by cultivation, the results are : — [1.) The 

 rains are absorbed by the loose soil as they fall, and, being percolated 

 gradually through it to considerable depths, are retained and diffused 

 over the country in small streams. (2.) The water being absorbed by 

 the soil, more vapour is generated in the surrounding neighborhood, and 

 consequently the air becomes more moist, and forms an attraction for 

 rain clouds ; thus more rain falls upon the ground than formerly ; and 

 (3), the rain being taken into the soil and given out gradually as ex- 

 plained above, the accumulation of large bodies of water by it when 

 heavy showers take place is reduced to a minimum, '/'herefore, it will 

 be found that as the country becomes more settled, and a greater extent 

 of its surface is broken up, so in proportion wiU the chances of sudden 

 floods be reduced. 



- Secondly, as to the effects which large masses of trees have in the 

 mitigation of floods. These are (1) by the shelter and annual deposit 

 of vegetable matter to the soil, this is rendered looser on the surface, 

 and of a more absorbent nature, and thus when rains come the water is 

 quickly taken into the gi-ound, and is given ofi" gradually in the form of 

 a watery vapour, e:^haled from the leaves of the trees, and by the means 

 of small streams. In this way, in the immediate neighborhood of ex- 

 tensive tracts of forest country, the danger of sudden floods is very much 

 diminished. As an illustration of the very absorbent natui-e of the soil 

 which is shaded by trees, I would instance the extensive forests of 

 Canada as a case in point, where I have seen it rain heavily for ten 

 hours at a time, and still there would not be any appreciative rise in the 

 rivers.' Here, then, we see that instead of a destructive flood arising, 

 the rain was stored up in the earth for supply during dry weather. In 

 the early days of American settlement, when the country was densely 

 covered with forests, such a thiag as a flood was but little known. Now, 

 however, in those parts of the country where extensive clearances have 

 •taken place withm the last century, floods of fearful magnitude occur 

 which are the means annually of sweeping off himdi-eds of Uves and 

 thousands of pounds' worth of property. 



I cannot but quote here from an excellent essay written by an 

 Amencan lately on this subject.—" Now, a body of timber is especially 

 adapted for the retention of the rainfall. Suppose twelve inches of 

 water ±aUs m an open country, and the same amount in a forest in twenty- 

 four hours. In the former instance, though the ground may be di-v it 

 IS impossible for it to take in this amount— probably not more than four 



