ly in language; it occurs where the organs of speech find
themselves helped by changing a letter for another which has just
occurred, or will just occur in a word; thus we say not '_adf_iance'
but '_aff_iance', not 're_n_ow_m_', as our ancestors did when the word
'renommee' was first naturalized, but 're_n_ow_n_'. At the same time
there is another opposite process, where some letter would recur too
often for euphony or comfort in speaking, if the strict form of the word
were too closely held fast, and where consequently this letter is
exchanged for some other, generally for some nearly allied; thus it is
at least a reasonable suggestion, that 'coe_r_uleum' was once
'coe_l_uleum', from coelum: so too the Italians prefer 've_l_e_n_o' to
've_n_e_n_o'; and we 'cinnamo_n_' to 'cinnamo_m_' (the earlier form); in
'turtle' and 'purple' we have shrunk from the double '_r_' of 'turtur'
and 'purpura'; and this process of _making unlike_, requiring a term to
express it, will create, or indeed has created, the word 'dissimilation',
which probably will in due time establish itself among us in far wider
than its primary use.

'Watershed' has only recently begun to appear in books of geography; and
yet how convenient it must be admitted to be; how much more so than
'line of water parting', which it has succeeded; meaning, as I need
hardly tell you it does, not merely that which _sheds_ the waters, but
that which _divides_ them ('wasserscheide'); and being applied to that
exact ridge and highest line in a mountain region, where the waters of
that region separate off and divide, some to one side, and some to the
other; as in the Rocky Mountains of North America there are streams
rising within very few miles of one another, which flow severally east
and west, and, if not in unbroken course, yet as affluents to larger
rivers, fall at least severally into the Pacific and Atlantic oceans. It
must be allowed, I think, that not merely geographical terminology, but
geography itself, had a benefactor in him who first endowed it with so
expressive and comprehensive a word, bringing before us a fact which we
should scarcely have been aware of without it.

There is another word which I have just employed, 'affluent', in the
sense of a stream which does not flow into the sea, but joins a larger
stream, as for instance, the Isis is an 'affluent' of the Thames, the
Moselle of the Rhine. It is itself an example in the same kind of that
whereof I have