304 EFFECTS OF FORESTS UPON CLIMATE: MAURITIUS. 



is excellent, and the garrison and ships visiting the island are supplied 

 in abundance with vegetables of various kiuds.^ 



South Africa. 



In South Africa, the most disastrous effects are felt frona droughts, 

 and from inundations following sudden and heavy falls of rain. It ap- 

 pears from evidence that these conditions have changed greatly within 

 the historic period, and that they tend to grow^ worse from year to year. 

 This subject has been very fully discussed by the Kev. J. C. Brown, for- 

 merly colonial botanist,^ who arrives at the conclusion that this arid- 

 ity has been promoted by the destruction of vegetation, removing au 

 important screen which throws off or absorbs the direct rays of the Pun, 

 and one w^hich in other ways conserves the humidity of the soil and of 

 the atmosphere. He urges a discontinuance of burning over the surface; 

 the adoption of enlighteuod measures for the conservation and extension 

 of forests ; the construction of reservoirs for retaining the excessively 

 abundant waters after heavy rains ; and the using of these waters for 

 purposes of irrigation. The fall of rain in torrents instead of drizzling 

 showers, and its drainage from the surface by short-lived floods instead 

 of eq.uably flowing streams, he regards as characteristics of lands divested 

 or devoid of vegetation, and hence any measures tending to cover the 

 surface with trees or herbage must be followed by good results. 



Since the publication of the work above cited, more recent damages, 

 not mentioned therein, have occurred in South Africa from these causes. 

 Toward the close of 1874, according to colonial newspapers, damages 

 occurred from floods which could not be estimated at less than £300,000, 

 and from one report the injury to public works alone was estimated at 

 £350,000.3 



Mauritius. 



Attention has of late years been called to the climatic conditions of 

 the island of Mauritius, following the clearing off of forests, that deserve 

 notice in this connection. This island lies in the torrid zone, exposed 

 to the trade winds of the Indian Ocean, and has an area of about 720 

 square miles. It was originally covered with dense forests, but the 

 cultivation of the sugar-cane being found extremely profitable, extensive 

 clearings have been made since 1851, resulting in changes that have 

 excited grave apprehensions, and have led to careful inquiries. A gov- 

 ernment observatory has existed for a long period, but several changes 

 of location render comparisons uncertain. These records, so far as they 

 can be used, show that the absolute and relative humidity, as well as 



1 Brown's Forcsis and Moisture (1877), pp. 128-14"3. 



-Hydrohgij of South Africa; or Details of the former hydrograpUc condition of the Cape 

 of Good Hope, and of Causes of its present Aridity. Lonflon, 1675, 8 vo., p. 260. 



3Iu a njore recent work by Mr. Brown (Forests and Moisture, 1877, p. 148), a striking 

 illustration of the local efiect of trees is raentionetl, from a correspondence bad in 

 1884-'65. " Tbis season bas been unusnally bot and dry along tbe coast, and all around 

 Grahamtown we bave been unable to grow anything all tbis summer for waur of rain. 

 Tbe springs are all failing. You may, perbapa, know tbe place of Mr. J. J. Stone, ou 

 tbe top of tbe bill ou tbe Cowie Road, toward tbe sea, marked out by a quantity of 

 gum trees, on tbe ridge of tbe bigb bills to tbe southeast of Grabamtown. Well, all 

 tbrougb tbe summer wo bad only ligbt, misty rain, just enough to dampen tbe grass, 

 and not enough to wet tbe ground; buttbese trees of Mr. Stone's have there converted 

 tbe mist into rain. They bave scarcely felt any etfects of dry weather; the vegeta- 

 bles and flowers have there grown all the summer -without watering; there the tanks 

 bave always been full ; and that is tbe only place of which I bave beard, tbat it bas 

 been so within five and twenty miles of Grahamtown." 



