Book III. CLASSIFICATION OF TREES. 941 



horse-chestnut. Resinous timbers are the pine and fir tribes. Brittle timber is exemplified m acacia, horn- 

 beam, and spindle-tree ; flexible, in the ash, broad-leaved elm, and chestnut ; smooth-grained, in the lime, 

 poplar, willow, hornbeam ; coarse-grained, in the ash, oak, and chestnut ; plain-colored, in the willow, lime, 

 holly ; and variegated, in the yew, thorn, walnut, elm, plum, and many others. 



6785. Bark, which contains the tannin principle, is an important product of trees. 



That which affords it in greatest quantity is the oak ; and next, as far as chemists have 



yet ascertained, the Leicester willow (Salix alba, var.), Spanish chestnut, ash, sloe, Lom- 



bardy poplar, hazel, elm, common willow, sycamore, beech, horse-chestnut, birch, and 



larch. (659. & Agr. Client. 89.) 



6786. Charcoal, which is made from either branches, trunk, or roots, has been afforded by different trees 

 at the following rates per cent. ; laburnum, 24 5 ; chestnut, 232 ; oak, 226 ; walnut, 206 ; holly, beech, 

 maple, 199; elm, 195; Norway pine, 192; sallow, 184; ash, I7 - 9; birch, 17*4; Scotch pine, 164. 

 (Agr. Chem. 105.) Proust found the greatest proportion of charcoal to be afforded by the ash. (698.) 



6787. Ashes have been afforded by the oak at the rate of 15 ; elm, 39 ; beech, 12 ; and poplar, 7 parts in 

 ten thousand. (Agr. Chem. 113.) The result of Saussure's experiments, on procuring ashes from trees, have 

 been already related. (703.) 



6788. For fuel and fencing. The tendency of trees to produce lateral branches, and 



renew them when lopped off, is an important quality, and exists in an eminent degree in 



the ash, elm, oak, willow, poplar, lime, &c. ; but not at all in the pine and fir tribes, and 



but slightly in the plane, walnut, and some others. Those which grow most rapidly are 



also to be desired as fuel-trees, as the acacia, poplar, willow, in most soils ; and the larch 



fir, Scotch pine, and birch, on such as are dry. The ailanthus glandulosus may also be 



mentioned as a bulky and rapid-growing tree. On the chalky hills at Mereville (before 



the revolution one of the most extensive parks and magnificent seats in France), this tree 



thrives, and attains a considerable size, where few others will grow. 



6789. For hoops, basket-willows, besom-spray, implement-handles, poles, &c. the renewal of trees or shrubs 

 which have been cut down, or technically, their tendency to stole or shoot out from the collar, is an im- 

 portant consideration. This quality does not belong to the pine and fir tribes ; and only slightly to the 

 beech, sycamore, alder, plane, &c. ; but liberally to all those mentioned above, as renewing their branches, 

 and indeed to most trees not resinous. For the same objects, the tendency of trees to send up suckers or 

 root-shoots deserves also the attention of the planter. This never takes place with the resinous trees, and 

 seldom with the oak, beech, chestnut, ash, plane, &c. ; but it is general with the elm, poplar, acacia, 

 primus, pyrus, mespilus, lime, and several willows. 



6790. For shelter, rapid-growing and evergreen trees are desirable, as the Scotch pine ; 

 and such as are at the same time clothed with branches from the ground upwards, as the 

 spruce fir ; the best of all trees for shelter, unless the situation is very elevated. Among 

 the deciduous trees, the fast-growing branchy sorts are most desirable, as the larch, birch, 

 poplar, willow ; in very elevated situations, the birch, mountain ash, and Scotch fir ; ex- 

 posed to the sea-breeze, the elder and sycamore. To maintain a branchy leafy screen 

 from the ground upwards, intermix trees and shrubs which stole ; or such as grow under 

 the shade and drip of others, as the holly, hazel, dogwood, box, yew, &c. To produce 

 shelter, and yet admit of the growth of grass below the trees, prune any sort to single 

 stems, and use chiefly deciduous sorts. 



6791. For shade, close plantations are seldom desirable, a free circulation of air being necessary to cool- 

 ness ; therefore use trees with lofty stems and large heads, and prune them to single stems a certain height, 

 as the oak, elm, chestnut, beech, for thick shade ; the plane, acacia, poplar, for lighter shade ; the birch, 

 balm of Gilead fir, and lime, for odoriferous shade; and avoid the walnut, elder, and laburnum, the atmo- 

 sphere under which is reckoned deleterious. 



6792. For improving bad soils, and for all the purposes of planting, the soil and situation, affected by or 

 natural to trees, is an important study for the planter. Some are aquatics, or delight in moist situations 

 near water, as most of the willow and poplar tribes, the alder and elder ; others are mountain trees, as the 

 Scotch pine, larch fir, mountain ash, sorb; some delight in valleys or plains, as the narrow-leaved elm, 

 horse-chestnut, plane, lime, oak ; others, in craggy steeps and dells, as the ash, silver and spruce firs, most 

 of the pines, and many more ; some on chalky soils, as the beech ; others on clays, as the oak ; on sand, 

 as the Scotch pine ; and a few trees will grow in the most opposite situations and soils, as the elder, which 

 is found on mountain tops and on the sea-shore ; the birch on the highest mountains, on dry rocks, and on 

 marshes. For the poorest soils, whether high or low, choose the birch, larch, and Scotch pine; and for 

 the richest, the ash, elm, oak, chestnuts, limes, poplars, and willows. 



6793. For the purposes of the separation of, or defence from, the inferior animals, the plantations called 

 hedges, or close rows of shrubs, are adopted ; when these are to be low, such shrubs as send out numerous 

 branches from the root upwards, and are of great durability, are most desirable ; as the holly among ever- 

 greens ; and the hawthorn, sloe, crab, beech, buckthorn, and hornbeam, among deciduous sorts. For moist 

 situations, the alder, elder, birch, and willow, are to be preferred ; and for dry upland sites, the juniper, 

 whin, birch, and elder : avoid poisonous trees, as the yew. For tall or tree hedges, such trees as the elm, 

 beech, hornbeam, lime, birch, and spruce fir, are desirable; but the holly excels all other plants for a 

 hedge, whether low or tall, and is liable to no other objection than its slow growth, which occasions a con- 

 siderable expense in protecting it till it is able to serve for defence. 



6794. For seclusion and concealment, branchy leafy trees, a number of which have been mentioned 

 (6790.), are obviously desirable ; and, for distinction, either sorts different from what are already there, or 

 ordinary sorts pruned and made to assume extraordinary forms. 



6795. For the various purposes of ornament, beauty, or effect, in landscape, the hardy 

 trees may be arranged as to magnitude, form, mode of growth, duration, and expression. 



6796. Magnitude. Trees of great height are, the English elm, ash, larch, Polish and 

 Carolina poplars, &c. ; but the laburnum, mountain ash, and evergreen oak, are very low 

 trees. A medium in height may be found in the maple, pine, and birch. Some trees 

 exceed in breadth, as the oak, Spanish chestnut, and Scotch elm ; others of different heights 

 are very slender, as the Lombardy poplar, cypress, and bird-cherry. 



6797. Form. The oak and Spanish chestnut afford the most irregular and picturesque 



