These sounds are produced in the middle, at the back, and at the front of the mouth respectively. These localities, and something of the nature of the sounds themselves, as _slender_ or _full_, will be plainly illustrated by the annexed figure: 3. Front- 1. Middle- 2. Back- Mouth Mouth Mouth ou i e (^a) a; _o_ _u_ The following description of the organic formation or production of these sounds now becomes important. The Vowel-Sound I (ee) is the most slender and condensed of the Vowel-Scale. It is produced at the middle or central part of the mouth, by forcing a slight, closely-squeezed current of Sounding Breath, through a small, smooth channel or opening made by forming _a gutter or scoop of the flattened point of the tongue_; while, at the same time, the tongue is applied at the edges to the teeth and gums. This sound has, therefore, an actual _form_ resembling that of a thread or line; or still better, like that of a wire drawn through one of the iron openings by means of which wire is manufactured. It resembles also a slight, smooth, roundish stream of fluid escaping through a tube or trough. This sound has relation, therefore, in the first place, to _Centrality_ or CENTRE; and then to LENGTH (or Line), which is the First Dimension of Extension. The I-sound continued or prolonged gives the idea of Length. But broken into Least Units of the same quality of Sound, we have individualized Vowel-Sounds of this quality, each one of which is a new _Centre_; like the successive _Points_ of which a _Line_ is composed.