BRITISH FOREST TREES 95 



clays, or on sandy soils apt to suffer from want of moisture. 

 When the climate is mild, and the period of vegetation 

 prolonged through warm spring and autumn weather, 

 plantations show rapid growth in youth, which, however, 

 does not always continue throughout the whole period of 

 rotation, but not infrequently shows signs of loss of energy 

 about the fortieth to sixtieth year. The too rapid develop- 

 ment during the youthful period produces soft wood of in- 

 different quality, which offers but little resistance to dangers 

 threatened by snow, by the attacks of insects, through 

 infection with fungous disease, or to diseases originating in 

 other causes. Although of course this is by no means 

 necessarily the case, it is not unusual to find such spruce 

 woods early interrupted in canopy, and unable to afford 

 sufficient protection to the soil, so much so in fact that their 

 clearance may be advisable before they have attained sixty 

 years of age. On such localities spruce is not necessarily 

 out of place, but may, grown in patches along with a ruling 

 species for which the soil and situation are more suitable, 

 attain very satisfactory growth, and assist very materially in 

 increasing the ultimate returns from the crop. The periods 

 of rotation of spruce usually vary from seventy to eighty 

 up to a hundred or a hundred and twenty years, the 

 former supplying the ordinary assortments of timber 

 requisite for building purposes, the latter yielding large 

 squares. Local demands of course to a great extent 

 determine the most remunerative period of rotation, but 

 where the forests are extensive, fixing the fall at an early 

 age is apt to swamp the market with small timber, whilst 

 entailing the harvesting of large quantities of top-ends and 

 small material of very little value. The postponement of 

 the fall to a hundred and twenty or a hundred and 

 forty years, for the production of large- girthed timber, can 

 only be advisable in very sheltered localities, owing to the 



