192 
NATURE NOTES 
clouds drifting through trees we notice, when they have passed, 
that the trees are wet and dripping : if the clouds are above 
the trees, other conditions being favourable, the vapour that 
constantly rises from every wood will (by the law of cohesion) 
detain them and uniting with them the clouds become over- 
charged and rain descends. Perhaps it cannot be truly said 
that trees bring rain ; but they, and the moisture that surrounds 
them and without which they do not exist, arrest the watery 
vapour in the atmosphere so as to cause rain to fall. Besides, 
by the law of gravitation, the moist vapour that lies in and 
hovers above the forest, must attract passing clouds floating in 
the surrounding atmosphere, and trees themselves must do the 
same to some extent. 
Living a mile from the sea, as I do now, and a few miles 
from the New Forest, clouds coming from the sea frequently 
drift through my garden, just wetting the trees without any rain 
falling, but on their reaching the forest there will be a downpour. 
Forests, it must not be forgotten, are of the greatest service 
to man in making leaf-mould, which when washed down to the 
lower levels produces fertile lands, as in the case of river deltas, 
or enriches a country as the waters of the Nile do, when they 
overflow and deposit a rich mud formed from leaves, mosses, 
decayed wood and such like. The wash down from bare hills 
is not only useless but destructive when it covers up land under 
cultivation. 
From what has been said it must be evident that if, under 
the impulse of civilisation, man entirely destroys the forest, 
except in special situations, he so ruins the climate and 
altogether causes such mischief that he destroys agriculture 
and makes the land unfit for human habitation. Yet this is 
exactly what has happened in a greater or less degree through- 
out nearly the whole world. 
Let us cast our eyes along those countries that are seen on 
the map surrounding the Mediterranean Sea, that central water 
that ever must be the common highway of civilised mankind. 
We commence with Spain, a country to which I particularly 
drew attention in my former paper (see Nature Notes for 
August, 1896), whose climate has been destroyed by the drought 
ensuing from the cutting down of the forests, and whose 
prosperity has steadily declined with the consequent failure of 
agriculture. The centre of the peninsula is almost treeless, 
alternate hot and cold blasts sweep unchecked over it, the fat 
of the land has evaporated and is not reproduced, the earth is 
dust. It may be fairly said that had Spain expended in the 
restoration of her forests the sums she has squandered during 
the last fifty years in the island of Cuba, she would already be 
seeing much improved days. Yet Spain is not the most back- 
ward country in Europe in the matter of forestry, that post of 
distinction belongs to a people that will be dealt with last. 
The Spanish have an excellent school of forestry at San 
Lorenzo del Escurial, near Madrid, and were sufficient funds 
