[From Manx Soc vol 2, Kelly's Manx Grammar]
A is ranked among the broad vowels; and in ancient manuscripts a, o, and u, are written indifferently one for the other; as clagh* or clogh**, a stone--goan or goun, scarce; thus, among the Latins, forreus is written for farreus, &c. It is pronounced as a English in man, pan, lad, bad; as, sap, lab, bab; and when circumflexed, as in dame, pale, ale; as mâroo.
B is a labial letter, and pronounced as b English; as, bare, boayl.
C preserves a strong sound in its unaspirated state, equal to the Greek Kappa, or the English k, or as c in can; as, cam, cab, cappan. It never usurps the pronunciation of s, as in cistern, city, cedar.
Ch has a soft sound; as in chingys, chiass, chaghter; like ch in English, in cherry, charcoal.
D is pronounced as d English; as doal, dowin. D and t are found in ancient manuscripts written indifferently one for the other; as y diunid, or y diunit, the profound.
E is reckoned a small vowel; but is sometimes long, sometimes short, and thus answers to the Greek Epsilon and Eta. When it is acuted, it is pronounced as e English in men; as ben, shen, ren; circumflexed, as ea in fear; as mêriu.
F is called a weak consonant; because when aspirated it loses all its force; as fer-ynsee, a teacher, e er-ynsee, his teacher. It corresponds in many cases with the Latin v; as fer, a man, Lat. vir; feeyn, wine, Lat. vinum; fockle, a word, Lat. vocalic, and is pronounced as f English; as faase, foays.
G is a heavy consonant; and pronounced as the Greek Gamma, or as g English in gain, get, go; as gamman, goaill, garrish. It has no soft sound, as in the English gentle.
H is pronounced as h in the English hand, hind. Note.--Some would rather call this an auxiliary than a letter, because it serves only to aspirate the foregoing consonants; as ch, ph, th, or the following vowels, as ha, he; and in nouns of the feminine gender beginning with a vowel, though not always written, is always strongly expressed; as e eddin, her face, pronounced as if written e heddin.
I is one of the small vowels, and pronounced as i English in pin; as shillish, shimmey, shid.
L is a letter which admits of no aspiration. When it begins feminine noun it is pronounced liquid and double, though written single, as e laue, her hand, pronounced el laue or e llaue.
M is naturally one of the strong consonants, but is often changed into its soft v. It is pronounced as m English.
N as n English. It is never aspirated nor eclipsed; and is called a light consonant. It is often doubled, to give the stronger sound. In nouns plural, and feminines, n is pronounced like gn in seigneur; thus, e niart, her strength, is pronounced en niart; nyn yannoo, our doings; nyn nyannoo.
O is a broad vowel. When acuted, it is pronounced as o in gone; thus, cron, son; when circumflexed, as o in bone; thus, ôney. And thus it answers to the Greek Omicron and Omega.
P is a hard consonant, and pronounced as p English.
Ph as the Greek Phi; or ph English, in philosophy, physic; as phadeyr, phaal.
R is a light consonant, and pronounced as r English; as maroo, sarey; but when an initial, it is always aspirated as the Greek Rho, as if it were written rh, and is pronounced double (rr), like l and n in feminine and plural nouns.
S as s in the English savour, sense; as saggyrt, sollan; and is called the queen of consonants, because it is subject to no change, like the Greek Sigma, suae potestatis litera, except it be followed by a vowel, or of the feminine gender, and then it suffers a change, vid. Chap. III.
T is a hard consonant, naturally commutable with the letter d (as has been already observed). It has been much abused and corrupted in modern manuscripts, &c., and ch often substituted in its place, entirely destroying the Celtic root; as chengey, a tongue, for teanga, Irish; chiarn, a lord, for tiearn, Irish; cum multis aliis.
U is one of the three broad vowels, and used indifferently for a and o; as goll, or gall, or goul, a fork or ray.
V is not properly a radical consonant, but only a secondary mute; however, we have some words which begin with v as a radical, therefore it is admitted as such; as vaidyn, a while ago, varrey mish, I warrant, voalley, a wall.
W is pronounced as oo, as in boot; as bwaoaill, wardoon, warp, warree.
Y is pronounced as u in the English turn, hunt; or as i in bird, third; as spyrryd, ymmyrchagh. Alone, as forming the article y, it has the sound of e in the English met.
* Northside pronunciation.
** Southside pronunciation.