which excite in us the sensation of smell, show that these par¬ 
ticles, which may be considered with regard to the tree as fe«, 
culent matter, sometimes extend their influence to an astonish¬ 
ing distance.* Nature, by rejecting them, plainly proves 
that they are baneful to vegetation. On this account, trees 
which have been planted by themselves in a favourable situa¬ 
tion, have almost in every case a finer appearance, and their 
timber is more perfect than that of such as grow in forests. 
Whenever any of the latter acquire strength, they cause the 
contiguous ones to perish, that they may at the same time find 
room to extend their roots and get rid of the effluvia which 
incommode them. A clump of trees will often shoot up to a 
great height; the reason is, that the trees being in part de¬ 
prived of nourishment of the atmosphere, hardly receive the 
light but at top; this element being equally necessary to their 
own growth, and causing the gi-eenness of the leaves. But 
this portion of light not being sufficient to keep them healthy, 
they gradually decay, the lateral branches are withered up, 
and the trunk, by being deprived of the genial influence of 
the sun, becomes weak and slender.' 
But to draw some inferences from the principles which we 
ihave just laid down :—The more the boughs are liable to bend 
down and assume a horizontal direction, as is commonly the 
case with those of the apple tree, at the greater distance ought 
the plants to be placed from each other. By such a practice 
they are more exposed to receive the mild heat of the sun, 
and to enjoy a wholesome air, and their fruit ripens better. 
The grass under is of a better quality, and when the ground 
is sown for grain, it produces better and more plentiful crops. 
There is also another advantage attending it, which is, that 
when the trees have got old, and yield but an indifferent pro¬ 
duce, an orchard may be replanted without any inconvenience, 
by placing the young trees between every other of the old 
ones, and in a few years be renewed. 
* We are assured by voyagers of credit, that in their passage to the East 
1'ndies, they have distinctly smelled the aromatic scents of Ceylon at the 
distance of more than fifty miles. 
i , 
\ 
CHAPTER 
