and migrations are now very rare: but there are other causes of
change, which, though slow in their operation, and invisible in
their progress, are perhaps as much superiour to human resistance,
as the revolutions of the sky, or intumescence of the tide. Commerce,
however necessary, however lucrative, as it depraves the manners,
corrupts the language; they that have frequent intercourse with
strangers, to whom they endeavour to accommodate themselves, must
in time learn a mingled dialect, like the jargon which serves the
traffickers on the Mediterranean and Indian coasts. This will not
always be confined to the exchange, the warehouse, or the port,
but will be communicated by degrees to other ranks of the people,
and be at last incorporated with the current speech.

There are likewise internal causes equally forcible. The language
most likely to continue long without alteration, would be that of
a nation raised a little, and but a little above barbarity, secluded
from strangers, and totally employed in procuring the conveniencies
of life; either without books, or, like some of the Mahometan
countries, with very few: men thus busied and unlearned, having only
such words as common use requires, would perhaps long continue to
express the same notions by the same signs. But no such constancy
can be expected in a people polished by arts, and classed by
subordination, where one part of the community is sustained and
accommodated by the labour of the other. Those who have much leisure
to think, will always be enlarging the stock of ideas, and every
increase of knowledge, whether real or fancied, will produce new
words, or combinations of words. When the mind is unchained from
necessity, it will range after convenience; when it is left at
large in the fields of speculation, it will shift opinions; as any
custom is disused, the words that expressed it must perish with it;