173 
Monpay, Fresruary 12TH, 1855. 
JOHN ANSTER, LL. D.; in the Chair. 
Tue Rev. Robert Carmichael, F.T.C.D.; Alexander Carte, 
M.D.; and the Rev. Ogle William Moore, were elected Mem- 
bers of the Academy. 
Professor Downing read a Paper on the draining of the 
Haarlem Lake. 
The lake of Haarlem, situated in North Holland, con- 
tains 44,500 acres, which, previous to its drainage, was covered 
with a depth of thirteen feet of water, the surface of which 
was under the mean tide level of the sea ; it is now completely 
dry and under cultivation. 
To have an adequate idea of the difficulties encountered in 
bringing this work to a suceessful termination, it is necessary 
to consider the peculiar physical and artificial circumstances 
of the Netherlands. The greater portion of the surface is at 
or below the level of the sea, and only protected from being 
again covered with water by immense dykes, which guard it 
alike from the rivers and the sea. Along the greater portion 
of its western boundary, it is, however, in a great degree 
protected by the dunes or sand-hills which form the coast line. 
The rise of tide along the coasts of the Zuyder Zee is only 
two feet, and upon the west, in the German Ocean, it is six 
feet, the mean level being very nearly the same. The annual 
rain-fall, as deduced from observations continued for nearly one 
hundred years, is on the average 25-15 inches; the mean annual 
evaporation is22°6 inches, distributed, however, very unequally 
in the winter and summer seasons, thus : 
Summer. Winter. Total. 
Fall of rain, . 105in. . 1465 in. . 25:15 in. 
. Evaporation, . 15°9,,  : 167 °,,  «' 22:6>.,, 
-5-4in. . +795in. . =2°55in. 
VOL. VI. Q 
