we must admit a twofold intonation for the flatus or the sibilants also. A flatus or spiritus cannot be modified exactly in the same manner as a consonant produced by contact; but, by an analogous process, it may become either "asper" or "lenis," sharp or soft. We are best acquainted with this distinction in the guttural, or hardly guttural, flatus at the beginning of words. The spiritus asper and lenis in Greek are modifications of that initial breathing which is inherent in every vowel sound at the beginning of a word or of a syllable. It comes out free as the spiritus asper in Homer and hiss, while it is tempered and to our ears hardly audible in ʼAristotle and ʼear. In ancient languages the spiritus asper is frequently represented by the dental flatus (s), and the spiritus lenis by the labial flatus v (Digamma Æolicum).
The dental flatus, as a tenuis or rather as spiritus asper, is heard in sin and seal; while media or lenis is frequently represented by the English z, as in zeal and breeze.
The sharp labial flatus is the pure f, which the Greeks could not pronounce, and which we hear in "find" and "life." The flat corresponding sound is heard in "vine" and "live." This also is a difficult letter to pronounce, and is therefore avoided by many people, or changed into b, as Scaliger said, "Felices populi quibus vivere est bibere."
Strictly speaking, and in accordance with our own definitions, every consonant at the end of a word, unless it is followed by a slight vocal exhalation such as is heard in drug, loud, sob, must become a tenuis. Now, if we take words where the final consonant is a flatus, but where, by the addition of a derivative syllable, the flatus ceases to be really final, we shall see distinctly how the flatus asper and lenis interchange. The guttural flatus cannot occur at the end of words. But the sharp dental flatus is heard in "grass" and "grease." Here the s is really final, although an e is put at the end of grease. If we form the two verbs, to graze and to grease, we have the corresponding flat s, the common German s. Exactly the same grammatical process applied to the labial flatus changes "life" into "live," i. e. the sharp labial flatus into the flat.
Some languages, as, for instance, Sanskrit, acknowledge none but sharp sibilants; and a media followed by s is changed in Sanskrit into a tenuis.
