i877-J 
The Balance of Nature. 
149 
both to each other and to the soil and the climate of their 
locality. Writers holding this opinion have even likened 
the various animal and vegetable species to the wheels and 
pinions of some delicate and complicated piece of machinery, 
none of which can be removed without injury to the whole. 
Man’s true policy, therefore, is to let Nature alone. The 
more he interferes the less reason will he have to he satis- 
fied with the results. It must he owned that far too many 
fats lend plausibility to this view. In nothing has man 
shown a more glaring want of prudence than in the wars he 
has waged against the lower animals ; but he cannot, how- 
ever willing, leave the balance of Nature undisturbed : he is 
compelled, by the law of self-preservation, to extirpate such 
carnivorous, venomous, parasitical, or otherwise destructive 
species as are dangerous to himself, his cattle, or his crops. 
Singularly enough, his appliances for waging war against 
such creatures have been developed far less rapidly than his 
means for the destruction of his fellow-men. But this is 
not all : he brings with him, in some cases by design and in 
others unintentionally, animals and plants which soon exert 
a powerful modifying influence. He is almost invariably 
accompanied by the grey rat, which at once goes to work to 
revolutionise the indigenous fauna. The small birds which 
have hitherto built in security on the ground, or in low 
trees, have their eggs and young carried off and devoured ; 
the lizards and the terrestrial Mollusca are attacked on the 
land, and the smaller fishes in the streams. Apterous in- 
serts, and the pupae and larvae of winged kinds, are sought 
for in all their haunts by the energetic destroyer ; and entire 
species are thus erased from the muster-roll of Nature. 
Such is the inevitable result where the rat is kept in check 
neither by serpents, birds of prey, nor carnivorous beasts. 
As an instance we may take Mauritius, where rats have 
multiplied to a frightful extent, and where the present 
poverty of the fauna, especially in insets, is notorious. 
But the animals which man introduces intentionally, and 
for his own use, are perhaps equally destructive. Foremost 
in this respet stands the goat ; he browses away the shrubs 
and the young seedling trees, and thus ultimately extirpates 
the woods. With the trees perish the insets ; and with the in- 
sets, fruits, and seeds the birds disappear also : the destrut ion 
of the aboriginal vegetation of St. Helena — a loss deeply felt 
by all students of organic geography — must be, in the main, 
ascribed to the ravages of goats. Swine take a prominent 
part in the work of destrution, and are particularly busy in 
eradicating all vegetables with bulbous or tuberous roots, or 
