4 
forests and forest trees in localities where are found the 
sources of creeks, rivers, and the supply of water to lakes 
and other fresh waters. 
For Great Britain this question has its greatest signifi- 
cance with regard to future forest culture on barren heights 
and the cultivation of shade and shelter trees along water- 
courses. The greatest part of the forest land with which our 
question has to deal is in the possession of large land- 
owners, but as far as I can ascertain there are no laws in 
existence giving a guarantee for the preservation and 
proper management of these forests. Far more importance 
has this question for the British Colonies, America, and 
several other countries, where either the State, a number 
of persons, and in some cases nobody, owns the land in 
question. 
That the forests regulate the flow of the water in water- 
courses, and ensure a steady supply during dry seasons, 
while they prevent sudden and disastrous floods, is a fact 
so often discussed and proved, that I need only refer to 
it here: 
That the forests also increase the rainfall has often been 
disputed, and this question has of late years received con- 
siderable attention, particularly in France, but there is still 
a great deal of uncertainty about the exact extent of the 
effect of a forest on the rainfall, and it is only by very minute 
observations of forests, consisting of the same species of 
trees in various altitudes, that series of trustworthy results 
can be attained. Still there is no longer any doubt as 
to the effect of the forest in conserving the water that falls, 
or that the humidity of the air above a forest is considerably 
larger than that of the airof the opencountry. Experiments 
in the South of France showed that the rainfall in a forest as 
compared with that in the open country was in the propor- 
