eat world. Already a remarkable shrew-mouse and
two native species of rat, peculiar to the island, have disappeared.
Dr. Andrews ("Proceedings of the Zoological Society," February 2nd,
1909), who has twice explored the island, gives evidence that this is
caused by a parasitic disease (due to a trypanosome like those which
cause sleeping-sickness and various horse and cattle diseases)
introduced by the common black rats from the ships which now frequent
the island. The further progress of destruction will be carefully and
minutely observed and recorded--but not arrested!

It is, however, in cutting down and burning forests of large trees
that man has done the most harm to himself and the other living
occupants of many regions of the earth's surface. We can trace these
evil results from more recent examples back into the remote past. The
water supply of the town of Plymouth was assured by Drake, who brought
water in a channel from Dartmoor. But the cutting down of the trees
has now rendered the great wet sponge of the Dartmoor region, from
which the water was drawn all the year, no longer a sponge. It no
longer "holds" the water of the rainfall, but in consequence of the
removal of the forest and the digging of ditches the water quickly
runs off the moor, and subsequently the whole countryside suffers from
drought. This sort of thing has occurred wherever man has been
sufficiently civilised and enterprising to commit the folly of
destroying forests. Forests have an immense effect on climate, causing
humidity of both the air and the soil, and give rise to moderate and
persistent instead of torrential streams. Spain has been irretrievably
injured by the cutting down of her forests in the course of a few
hundred years. The same thing is going on, to a disastrous extent, in
parts of the United States. Whole provinces of the Thibetan borders of
China have been converted into uninhabitable, sandy desert, where
centuries ago were fertile and well-watered pastures supporting rich
cities, in consequence of the reckless destruction of forest. In fact,
whether it is due to man's improvident action or to natural climatic
change, it appears that the formation of "desert" is due in the first
place to the destruction of forest, the consequent formation of a
barren, sandy area, and the subsequent spreading of what we may call
the "disease" or "desert ulcer," by the blowing of the fatally exposed
sand and the gradual extension, owing to t