INFLUENCE OF SOIL ON TIMBER. 101 



ihowed subsequently, that by barking trees two or even three years 

 before cutting them down, the white external wood could be render- 

 ed nearly as hard and durable as the heart- wood of the tree. The 

 iccommendation of this procedure by these two distinguished men 

 has not been followed in France ; but ever since 1770 the Dutch 

 have adopted it, and it is now practised in many parts of England, 

 particularly in the royal forests. 



It is quite certain that the nature of the soil exerts a considerable 

 influence on the rapidity of growth and quality of the timber. The 

 oak, the elm, &c., which have been grown in a damp soil, will not 

 be so hard and compact as the same trees reared on a dry plot. 

 Duhamel found, that although the trees which came in swampy bot- 

 toms were very sappy and wet, they were still lighter than others 

 of the same kind which had grown on a dry bank. Their white 

 wood is thick in comparison with their hard wood ; they are brittle, 

 and do not readily take or keep the shapes into which they are bent 

 for ship-bu'lding or for staves ; and then their pores being large and 

 open, and the whole wood being without that kind of varnish which 

 impregnates good timber, they are readily permeable and unfit for 

 the manufacture of vats, &c. — to say nothing of their being much 

 more perishable. Such soft and porous timber is altogether im- 

 proper for out-of-door constructions and for ship-building ; but it 

 answers extremely well for indoor and cabinet work ; for the latter 

 it has even certain advantages, it is easily wrought ; and once fairly 

 seasoned, it is neither so apt to warp nor to crack as harder wood. 

 It was very probably to guard against any excess of sap in trees, so 

 prejudicial in a general way to the timber they yield, that the Ro- 

 mans, according to Vitruvius, surrounded those that were destined to 

 be cut down with a trench six months beforehand.* 



Trees which have grown in a good soil sufficiently drained have 

 a fine bark, and their white wood is moderate or small in quantity. 

 Their woody layers, indeed, are apt to be thinner generally, than 

 those of trees that have grown in a wet soil ; but they are much 

 harder and tougher, their grain is more even and close, and their 

 pores are filled with an incrusting matter. They are consequently 

 very heavy, even when thoroughly dry, and with time and due 

 seasoning they become extremely hard, and in the same degree 

 acquire durability. Duhamel was led by his experiments to conclude 

 that the difference in point of density of timber grown in a marshy 

 soil, and in one that was well drained and dry, was occasionally in 

 the ratio of five to seven. 



The denser, dry-grown timber supports a relatively much greater 

 weight without breaking than the marsh-grown timber ; and when 

 it does yield, it gives way by a large and splintering surface, while 

 the softer, less dense wood snaps off short. In brief, there is na 

 question as to which kind of timber is the most valuable ; and meas- 

 ures ought to be taken by landed proprietors and timber-growers at 

 all times, not merely to grow trees, but to grow them under such cir- 



* Duhamel, Expl. de-^ bois t. i. p 46. 

 9* 



