THE VALUE OF WASTE LAND FOR AFFORESTATION PURPOSES. 149 
conditions, can be made to pay at all, as we shall see more 
clearly later on. 
INVESTIGATIONS ON TREE-GROWTH AND THE FACTORS OF 
LOCALITY. 
The above are the chief points to which attention should be 
directed in the first stages of inquiry. The next step constitutes 
the real work which investigations of this kind involve, viz., the 
attempt to ascertain the rate of tree-growth in the district. This 
work is attended with great difficulties, owing to the fact that 
not only are woods in such districts as we are considering often 
few and far between, but where they do exist, their condition is 
far from perfect, and they can rarely be regarded as fair examples 
of what the soil and climate are able to produce. To consider 
them alone would, therefore, seldom result in any satisfactory 
conclusions being arrived at, and in Great Britain, at any rate, 
we are obliged to extend our investigations to the soils and 
situations which the district presents to us bare of timber-trees, 
and which have probably never borne trees within the memory 
of man. 
TREE-GROWTH. 
Taking the former of these branches of investigation into 
consideration first, it is not difficult to realise its importance, and 
the great disadvantage of having to conduct our inquiries under 
existing adverse conditions. For without normal tree-growth to 
serve as a standard, it is practically impossible to ascertain the 
value of the local climate as a factor of growth, for however 
closely soils and situations may be studied, the effect of climate 
still remains an unknown factor in the development of timber- 
trees. 
On the Continent, and particularly in Germany, invaluable 
work has been done by the accurate measurement of sample 
areas of pure woodland of various ages, and growing on different 
soils and situations. By such measurements, which are made 
in the various forest districts throughout the country under 
precisely the same system of measurement, the effect of local 
climate can be seen to a tolerable nicety, and the development 
of different species followed without difficulty. With the aid of 
the “yield tables,’ thus obtained, the value of the land for 
sylvicultural purposes can be ascertained, and the period at 
