If, whenever there is a shower, you catch some rain-water, you will find
that it possesses all the properties which have been described. It will
be found to be an almost incompressible liquid, an imperial pint of
which weighs about a pound and a quarter. It would make no difference if
the rain-water were collected in Africa or in New Zealand; or if it had
been obtained centuries ago and kept bottled up ever since. And there is
every reason to believe that rain-water will have exactly the same
properties a hundred or a thousand years hence. So far as the properties
of rain-water are concerned =the order of nature is constant=.
This, however, is by no means the same thing as saying that the
properties of water are always the same. In fact the properties of the
substance, water, vary immensely according to the conditions to which it
is exposed; but, under the same conditions, they are the same, so that
we may still say that so far as water is concerned, the order of nature
is constant.