■z 5 a Dr. dobson’s Obfervations on 
than evaporated from the fame furface of water in 1774. 
Confequently the drynefs of the atmofphere or its power 
of folution, during the year 1775, exceeded that of 
1774 - 
2. If we take the medium of four years obfervations 
it appears, that the annual evaporation at Liverpool 
amounts to 36.78 inches. 
Dr. halley obferved at London, that water placed in 
a clofe room, where neither the winds or Sun could act 
upon it, exhaled only eight inches during the whole 
year. He makes no doubt but that the free accefs of the 
winds would have trebled the quantity carried away; 
and that this again would have been doubled by the 
alliftance of the Sun. Dr. halley, therefore, fixes the 
annual evaporation of London at 48 inches (a) . If this 
calculation be admitted, it follows, that the annual eva- 
poration of London exceeds the annual evaporation of 
Liverpool 1 1 inches ; but were the experiments to be 
made in London, in the fame cii'cumftances with thofe 
made at Liverpool, it is probable, that this would be 
found to be more than the real diffei'ence. 
The learned cruquius obferved at Delft in Holland, 
that there exhaled from water fet in the open air, but in 
a calm and fhady place, about 30 inches; and it is not to 
(a) Phil. Tranf* N° 21 2 * 
be 
