STUTP SOWING. 255 



insolation combined, some direction between the lines whose bear- 

 ings are respectively 0° and 45°. 



h. If against frost and a dangerous wind combined, some direc~ 

 tion between a line running north-east and south-west and the 

 perpendicular to the direction of the wind. 



c. If against excessive insolation and a dangerous wind com- 

 bined, some direction between a line running north ajad south and 

 the perpendicular to the direction of the wind. 



d. If against frost, excessive insolation and a dangerous wind 

 combined, some direction between that which would be followed 

 if only the first and second dangers acted together (case a above) 

 and that which would be adopted if only the second and third 

 (case c) or the first and third (case 6) were to be pro^aded against. 



In all four cases, the strips must of course follow most nearly 

 the direction required by the danger that was most to be preventedv 



§ 2. Length of the strips^ 



On level ground, the length of the strips may of course be indi-. 

 finite, being, hmited simply by the drainage channels and by the 

 extent of the area across which they run. But on. slopes it is 

 evident that they must be broken up into short lengths in order to 

 leave a sufficient number of intact intervals over which the main, 

 rush of surface drainage may pass without producing erosion. 

 The more broken the ground, the steeper the slopes, and the 

 heavier the rainfall on the higher ground above, the shorter must 

 be the strips and the longer the uncultivated gaps between. 



On hill-sides of varying slope certain strips may have to be dis- 

 continued altogether or new intermediate ones inserted according 

 as, with increasing or diminishing gradient, the distance between 

 two consecutive strips becomes insufficient or excessive^ 



§ 3. Distance- between the strips-^ 



The distance between the strips will depenji generally on the 

 time in which it is desired to produce a canopied growth, and this 

 will be influenced by several considerations as follows : — - 



(i) The quantity of useful forest growth already on the ground 

 capable of contributing, to a less or greater extent, towards its 

 formation. 



(ii) The rapidity of growth, in the given soil and locality and 

 under the given conditions of cultare, of the species to be sown. 



(iii) The shape and lateral extension of the crowns of young 

 individuals of those species. 



