658 Remarks on laying out 



logical arrangement is to be preferred. The geographical 

 arrangement is best carried into effect on the same description of 

 surface as is suitable for a scientific one. Whichever system 

 of arrangement is adopted, one main walk should be conducted 

 through the whole, so as to pass in review every individual tree 

 and shrub, and yet to show no plant twice. One of the best 

 modes of doing this, in an arboretum within an enclosure, is, to 

 plant the trees only on one side of the walk, and at different 

 distances from it; according to the heights which they are calcu- 

 lated to attain at that period when they will become too thick, 

 or, in other words, touch each other. Whatever this height may 

 be, provided it be greater than that of the human eye from the 

 ground, the tree or shrub ought to be placed at such a distance 

 from the walk as that the eye may see the top of it at an angle 

 of from 30° to 40°. A tree that grows 40 ft, high, or is expected 

 to attain that height before it is cut down, ought, according to 

 this calculation, to be placed about 50 ft. from the walk ; and a 

 shrub that grows 10 ft. high, about 10 ft. from it. Every shrub, 

 however low, ought to be placed at such a distance from the 

 walk as that its branches, when fully grown, may not reach nearer 

 to it than from 1 ft. to 2 ft. In an arboretum laid out in this 

 way, every tree and shrub will pass in review before the spectator 

 on one hand, as he walks along, without his being distracted by 

 the necessity of looking to both sides of the walk, and the con- 

 sequent fear of missing some specimen. If the space to contain 

 the arboretum is very ample, this principle may be joined to 

 that of displaying views of distant scenery, or forming glades 

 within the arboretum. Thus every order, or tribe, or genus, 

 may form one large group, the individuals composing it being 

 still at such distances as not to touch each other when fully 

 grown ; and the space between the orders, tribes, or genera, 

 may form open glades. 



Before planting, the ground ought to be deeply trenched, and 

 thoroughly drained, adding manure in considerable quantities, in 

 order to insure a rapid growth ; and introducing peat earth, 

 sand, and other soils suitable for particular genera or species, at 

 the time those genera or species are planted. The surface of 

 the ground, for 2 ft. or 3 ft. round each plant, ought to be kept 

 clear of weeds and grass, by hoeing or hand-weeding, for the 

 first five or six years ; but on no account ought it to be dug, 

 because that would prevent the roots from coming to the surface; 

 the consequence of which would be, that, being confined exclu- 

 sively to the moist cold soil below, the trees would be later in 

 sending out their leaves in spring, and in ripening their wood in 

 autumn. All the rest of the surface may be under grass, and 

 mown regularly ; the cut grass being laid round the roots of the 

 trees and shrubs as a mulch, to lessen evaporation and diminish 



