It is asserted by Pontoppidan, that rats cannot live further north
than Norway, and that those on the banks of the south side of the
river Vorman, very soon die if they are taken to the north, which he
attributes to the exhalations of the soil. From the Vicomte Querhoënt
I understand that rats multiplied so fast on their first introduction
to the isle of France, as even to compel the Dutch to leave it: they
have been somewhat lessened by the French, but they still remain in
great numbers. He adds, that when a rat has resided some time in India
he acquires a very strong smell of musk; and this is confirmed by M. la
Boullaye-le-Goux in his voyages. The Dutch voyagers also say that there
are scented rats in Madura.