As signs of this kind, one mark is as good as another; and instead of (-) we may, if we choose, substitute such a mark as (') (and write _n['o]t_=_n[=o]t_=_n[omega]t_=_n[=o]te)_; provided only that the sign (') expresses no other condition or affection of a sound. This use of the mark ('), _viz._ as a sign that the vowel over which it is placed is long (independent), is common in many languages. But is this use of (') natural? For a reason that the reader has anticipated, it is not natural, but conventional. It is used elsewhere not as the sign of _quantity_, but as the sign of _accent_; consequently, being placed over a letter, and being interpreted according to its natural meaning, it gives the idea, not that the syllable is long, but that it is emphatic or accented. Its use as a sign of quantity is an orthographical expedient, or a conventional mode of spelling. The English language abounds in orthographical expedients; the mode of expressing the quantity of the vowels being particularly numerous. To begin with these: The reduplication of a vowel where there is but one syllable (as in _feet_, _cool_), is an orthographical expedient. It merely means that the syllable is long (or independent). The juxta-position of two different vowels, where there is but one syllable (as in _plain_, _moan_), is an orthographical expedient. It generally means the same as the reduplication of a vowel, _i.e._, that the syllable is long (independent). The addition of the _e_ mute, as in _plane_, _whale_ (whatever may have been its origin), is, at present, but an orthographical expedient. It denotes the lengthening of the syllable. The reduplication of the consonant after a vowel, as in _spotted_, _torrent_, is in most cases but an orthographical expedient. It merely denotes that the preceding vowel is short (dependent). {189} The use of _ph_ for _f_ in _Philip_, is an orthographical expedient, founded upon etymological reasons. The use of _th_ for the simple sound of the first consonant in _thin_ and _thine_, is an orthographical expedient. The combination must be dealt with as a single letter. _X_, however, and _q_ are not orthographical expedients. They are orthographical compendiums. The above instances have been adduced as illustrations only. Further details will be found hereafter. For many of them we can give a reason (for instance, for the reduplication of a consonant to express the shortness of the preceding vowel), and of many of them we can give an historical account (see Chapter X.).