EXPERIMENTS ON EVAPORATION. 53 



it was found that the evaporatioa from the jar sunk in the cleared 

 ground had been more than double the evaporation from that which 

 was partially protected, though not covered by the bush ; the 

 former being 1-854 in.; the latter -863 in.; giving an excess of 

 "991 in. The experiment was repeated with similar results. 



In reporting these results Mf Blore remarked that had the experi- 

 ment been made in a more arid district, the evaporation would have 

 been greater ; and that had it been made in the open country, the 

 difference would have been marked. But, taking the results obtained 

 as the basis of calculation, he arrived, by the following process, at a 

 conclusion for which, probauly, few who have not given attention to 

 the subject are prepared. 



The excess of evaporation from the more exposed jar above that 

 from the jar partially shaded, but not covered, beiug one inch, more 

 strictly speaking upwards of ^f^J of an inch of water, and more than 

 doable that of the latter. " An inch in six days," says he, " will give 

 for 102 days, the ordinary duration of the hot windy and dry season 

 in the district, 17 inches. This is equal to about three hundred and 

 eighty-four thousand (384,000) gallons per acre, and supposing 1,000 

 acres to be burned, blackened, and di-ied — what with sunlight, fire, 

 heat, and wind, the evaporation would be an excess of three 

 hundred and eighty.four millions of gallons of water above what 

 would have been evaporated if the bush or grass had been left 

 unbnrued." 



In the prosecution of his researches, Mr Blore ascertained by 

 experiment that on Wynberg hill, while the deposit of dew on a 

 green surface amounted to 4-75, that on a white surface amounted 

 only to 2, showing that the deposit of dew upon a green surface is 

 more than double that upon a white ; and he further ascertained 

 that, while the difference of temperature in the water in the two jars 

 employed in the former experiment was only a few degrees, the 

 difference of temperature between black ground and ground shaded 

 by bush was about 25°, which would occasion a vastly greater 

 difference in the amount of evaporation than that which occurred in 

 his experiment. 



In a letter on planting trees by water-courses, appended to Report 

 of Colonial Botanist for 1863, it is stated: — "In the course of 

 my tour I have found that in some places an opinion prevails 

 that trees growing by the side of a stream, steal away the water. 

 And in support of this opinion, my attention was directed to the 



