112 Report 8. A. A. Advaxcemkxt of Scikxce. 



by the prevailing south-eastei-ly win Is, wliich become hotter and drier 

 as they ad\"ance northwards into lower latitudes.* It may be accepted 

 as a general rule that, with the exception of those rising in the dolomite 

 formation, the rivers can only be described as intermittent, torren- 

 tial streams flowing in deep channels that have not been eroded down 

 to base-level. At the end of the winter — May to September — they 

 are practically dry ; but in the wet season — October to April — ^the}- are 

 subject to violent floods that ox'ertop the banks. These freshets are 

 generally of short duration, and within a few days the rivers become 

 little better than dry water-courses. This is even true of such large 

 rivers as the Orange and the Yaal. Then, again, the country i;* 

 intersected by huge dongas into whicli the moisture of the surrounding 

 subsoil steadily percolates. One has only to see these dry ri\er beds 

 and dongas, from 10 ft. to upwards of 25 ft. deep, to realise the depth 

 and extent of soil that is drained by them. It was a stud}' of these 

 conditions — their cause, effect and remedy — that first drew the author's 

 attention to the influence of forests in preserving the natural water- 

 supply. The remedy lies in afl:brestation. 



Apart from the question of the timber supply, the appalling- 

 results of deforestation have perhaps contributed more than anything 

 else to impress scientific men with the value of forestry. Deforestation 

 causes : — 



General dessication of the country. 



Higher floods and a decrease of the permanent flow in rivers. 



Increase of temperature and evaporation. 



Drying up of springs. 



Silting of reservoirs, Arc, i^irc. 

 General Dessication. — Examples of dessication and sterility follow- 

 ing deforestation are to be found in many different countries. Renan, 

 writing on Phcenicia, attributes the depopulation of Syria to the 

 sterility caused by the destruction of forests. The trees cut down were 

 never replaced by others, and the summits of mountains that were 

 once covered with vegetable soil are now bare and arid. The case of 

 Cyprus is very striking. According to ancient authorities the island 

 was formerly covered with ti^ees. Vast forests of cedar crowned the 

 summits of the hills, whilst the lower slopes were clothed with a dense 

 growth of pine trees ; but these no longer exist, their only represen- 

 tati\es being a few scattered trees in confined areas. The whole of 

 the northern chain and the greater part of the most southern slopes 

 have been denuded, and either bare rock or unproductive thicket have 

 taken the place of the forests. The most valualile kinds — cedar.s, 

 cypresses and oaks — are only found in isolated clumps ; the treeless 

 heights no longer arrest the clouds, and the soil of the plain has 

 become parched and dry. The greater part remains uncultivated, and 

 a desert has replaced the ancient forests of C^'prus. It is claimed that 

 the island, through want of a natural water-supply, can now barely 



* See Rainfcdl of Sonth Africa (hirinri the Ten Years 1885-1894, by 

 A. P.uchan, M.A. 



