WOODS AND PLANTATIONS. 341 



want of moisture in the summer season is now being very much felt. 

 Showers of rain are indeed frequent, but from the want of the shade of 

 trees to keep the rays of the sun from drying the surface, the water is 

 evaporated at once without producing any lasting benefit to vegetation 

 or to the soil. In clearing these primeval forests, to be converted 

 into agricultural lands, large masses of them should be left on judi- 

 ciously-chosen sites, with the view of giving shelter, and also to be 

 the means of retaining moisture in the districts, and generally equal- 

 ising the climate, as there can be no doubt that the entire clearing 

 of forests is a great evil, and this is more especially the case in hilly 

 districts. 



At the present time there is a large tract of country in the imme- 

 diate neighbourhood of Cape Town which is very much dried up from a 

 want of moisture, and this is attributed to a general want of trees in 

 the district. Dr Brown of Haddington, late Colonial Botanist at Cape 

 Town, called attention to this fact in a report to the Colonial Government 

 in 1863, in which he states : 



I have found everywhere in the course of my tour, in the physical geography of 

 the country, what seenis to me to be indications that at a period not very remote this 

 must have been a land well watered everywhere ; and I have also found that within 

 the memory of the present occupants of the land there has been a remarkable change 

 in the aridity both of limited and of extensive districts. I have satisfied myself that 

 this is not a mere fancy, to be classed with the common saying in ancient and modern 

 times, that the former days were better than these. The fact is well attested ; and 

 I can refer to places both in the eastern and the western provinces where the change 

 was observed to follow immediately the destruction of bush, which is only in accord- 

 ance with what I would have expected. 



There is a widespread opinion that forests attract rain. I shall afterwards have 

 occasion to give a different account of the fact upon which this opinion is rested. At 

 present I rest satisfied with stating that what is done by forests on a large scale, is 

 done on a smaller scale by the bush, herbage, and grass of the veldt. If they do not 

 attract rain, they at least retain moisture; and the destruction of them allows that 

 moisture to be carried off. 



As I deem it of importance to produce a thorough conviction of this fact, which, 

 it appears, is not generally known, I may be allowed to enter at some length upon the 

 subject. 



It is well known that if a wet cloth be exposed in the air, it soon becomes dry ; or 

 if a quantity of water be left exposed in a basin, it soon disappears if the air be hot 

 and dry. Even the large reservoirs of water, if not replenished, dry up in the course 

 of time. In all these cases the water passes off in a state of vapour. This vapour is 

 transparent ; it is not like the cloud or mist, which consists of water in minute drops 

 suspended in the air. It is in a state of gas, and is as invisible as the air itself. 

 In accordance with the law of gaseous diffusion, which admits of unlimited diffusion 

 of one gas through another, the atmosphere is permeated with this vapour, which 

 may be found everywhere on the summit of the highest hills and at the bottom of 

 the deepest mines alike. It may have been observed that a glass of iced water is 



