56 TRANSACTIONS OF ROYAL SCOTTISH ARBORICULTURAL SOCIETY. 
appointed by it to consider “ whether the condition of our forests 
and woodlands might not be improved by the establishment of a 
forest-school.” The good intention of the promoters was not 
fulfilled, however. The committee did not meet. 
In the first instance, let me briefly refer to the national economic 
features of forests as they affect us. 
There are two aspects from which forests are of importance to a 
country—firstly, as a source of timber and fuel; secondly, on 
account of their hygienic and climatic influences. 
With regard to the latter, it is a popular notion that trees 
exercise considerable influence upon atmospheric conditions, but it 
is only within recent years, and as the result of long experimental 
research in Switzerland, France, Austria, Germany, and other areas 
where forestry is practised at a high level of excellence, and also in 
the United States, that any sufficient data have been forthcoming 
to form a basis of scientific conclusion upon so important a matter. 
Although many points are still far from clear, the evidence goes to 
show that the direct influence of tree-growth upon climate is no 
mere superstition. Stated in the most general terms, it is proved 
that forests improve the soil drainage, and thereby modify mias- 
matic conditions; whilst, like all green plants, trees exercise, 
through the process of carbon-assimilation, a purifying effect upon 
the air,—the existence of the increased quantity of ozone often 
claimed for the vicinity of forests is not yet established; by 
opposing obstacles to air currents, forests prevent the dissemination 
of dust particles with their contingent germs; they reduce the 
extremes of temperature of the air; they increase the relative 
humidity of the air and the precipitation in rainfall; and they 
protect and control the waterflow from the soil. 
To us these effects do not appeal with the same force that they 
do in Continental areas. Our insular and geographical position 
renders us in a measure independent of them. The data for these 
Continental results, it must be remembered, are derived from large 
forest areas such as do not exist here. For this country I know of 
no experimental evidence on the subject. As, however, the effects 
of forest influence are felt mainly in local modifications of climatic 
conditions, we are not justified in regarding the conclusions that 
have been reached as inapplicable to Britain. No little interest 
attaches, therefore, to a statement based upon these Continental 
observations to which Dr Nisbet has recently done well to call 
attention—that ‘“‘where the rainfall is over forty inches it is 
