[§ 227]. The combination tupt is stable, so also is the combination tuft. But the combination tupth is unstable: since the p is lene, the þ is a (so-called) aspirate. Hence arises a process of accommodation by which the word becomes either tupt or tufth (tufþ).

In respect to the unstable combination tupth, we may observe this, viz. that the ways of altering it are two. Either the first letter may be accommodated to the second, tufþ, or the second may be accommodated to the first, tupt. Which of these two changes shall take place is determined by the particular habit of the language. In Greek we add to the radical syllable τυπ-, the inflectional syllable -θην. The first letter, π, is accommodated to the second, θ, and the word becomes τυφθην (tyfþæn), as in ἐτύφθην (etyfþæn). In English we add to the radical syllable stag, the inflectional syllable s. Here the second letter is accommodated to the first, and the resulting word is not staks, but stagz.

[§ 228]. The Irish Gaelic, above most other languages, illustrates a euphonic principle that modifies the vowels of a word. The vowels a, o, u, are full, whilst i, e, y, are small. Now if to a syllable containing a small vowel, as buil, there be added

a syllable containing a broad one, as -am, a change takes place. Either the first syllable is accommodated to the second, or the second to the first; so that the vowels respectively contained in them are either both full or both small. Hence arises, in respect to the word quoted, either the form bualam, or else the form builim.

[§ 229]. In the words give and gave we have a change of tense expressed by a change of vowel. In the words price and prize a change of meaning is expressed by a change of consonant. In clothe and clad there is a change both of a vowel and of a consonant. In the words to use and a use there is a similar change, although it is not expressed by the spelling. To the ear the verb to use ends in z, although not to the eye. The following are instances of the permutation of letters.

Permutation of Vowels.

a to ĕ, as man, men.
a to oo, as stand, stood.
a to u, as dare, durst.
a to ē, as was, were.
ea to o, as speak, spoken.
ea=ĕ to ea=ē, as breath, breathe.
ee to ĕ, as deep, depth.
ea to o, as bear, bore.
i to a, as spin, span.
i to u, as spin, spun.
i=ei to o, as smite, smote.
i=ei to ĭ, as smite, smitten.
i to a, as give, gave.
i=ei to a, as rise, raise.
ĭ to e, as sit, set.
ow to ew, as blow, blew.
o to e, as strong, strength.
oo to ee, as tooth, teeth.
o to i, as top, tip.
o to e, as old, elder; tell, told.
ŏ to e, as brother, brethren.
ō=oo to i, as do, did.
o=oo to o=ŭ, as do, done.
oo to o, as choose, chose.

Permutation of Consonants.

f to v, life, live; calf, calves.
þ to ð, breath, to breathe.
ð to d, seethe, sod; clothe, clad.
d to t, build, built.
s to z, use, to use.
s to r, was, were; lose, forlorn.