Yan Yean Reservoir. 1/7 
where the rainfall is much greater than in the south of 
England, and the general temperature and atmospheric 
influences less favourable for the promotion of evaporation, the 
latter has been found by the Engineer of the Paisley Water- 
works and others to be less than in the southern counties of 
Great Britain. 
In the following table I have placed in juxta position the 
results arrived at by different observers. 
Evaporation 
from surface 
Mean | or difference 
annual |between rain- 
rainfall.|fall and avail- 
able supply. 
Remarks on nature of sur- 
face to which the observa- 
Anthority. Locality. a 
tions refer. 
Charnock | Ferrybridge 24-6 19:72 |Porous well drained soil 
Dalton | Manchester | 33-56} 25:15 |} O"dinary mould with 
2 
Howard oa 36° 30°47 { oan deed oe 
Small gathering grnd 
possessing well drain- 
Thom Paisley 54° 18° ed surface, watered by 
numerous catch-water 
drains. 
Beardmore | Bute 45-4 22°5 {Low country. 
4 nae . ‘ : Elevated district, 
Ditto Rivington Pike) 55°5 3173. { {EAB fe. ahonelaend 
Dickenson 26°6 15°64 |Ordinary porous soil. 
Charnock | Ferrybridge ese 32°60 |Moist undrained soil. 
Ditto Ditto oc 35°03  |Water surface. 
Dalton Manchester age 44:43 |Water surface. 
The inferences to be derived from an inspection of this 
table are,—first, that the values assigned to evaporation from 
land surfaces by these different authorities are, (with the 
exception of that given by Dickenson), quite compatible with 
each other if due allowance be made for the variations of the 
temperature, geological configuration, soil, and rainfall of the 
places of observation: and, secondly,—that when the annual 
rainfall exceeds the annual average quantity, the annual pro- 
portionate amount thereof evaporated does not also increase as a 
necessary consequence of such augmented rainfall. I may here 
remark that Charnock’s observations indicated at the least 
annual evaporation during the five years over which his ob- 
servations extended, had occurred during a year when the 
annual rainfall had been about the average of the five years. 
This shows the futility of assuming (as too frequently has 
U 
