The Scotch Gaelic is spoken in its greatest purity in the central districts of the Highlands, including Mull, Morvern, Ardnamurchan, Ardgowar, Appin, Lochaber, and that district termed the Garbh chriochan, or rough bounds, consisting of Arisaig, Moydart, Moror, and Knoydart. The language here spoken is characterized by a closer adherence to grammatical rules, by a fuller and more careful pronunciation of the vowel sounds, by a selection of the best words to express the idea, and by their use in their primary sense.

In the county of Argyll, and the islands which face the coast of Ireland, the language approaches much more nearly to the Ulster dialect of the Irish, there being probably no perceptible difference between the form of the language in Isla and Rachrin, or in Cantyre and the opposite coast of Antrim.

In the Gaelic of Sutherland and Caithness, again, there are marked differences of a different and opposite character, a native of Sutherland and the southern districts of Argyll having some difficulty in understanding each other; and in Perthshire, on the other hand, the influence of the English language is apparent, the pronunciation is more careless, the words selected less pure, and the secondary senses of many are only used.

The central districts afford the best type of that variety of Gaelic which forms the spoken language of the Highlands of Scotland.

Of this language two views may be taken. The peculiarities of the language may have sprung up quite recently, and the language may, at no very distant period, have been absolutely identical in form and sound with the Irish, from which it may have become corrupted by the absence of cultivation, and must be regarded merely as the rude patois of a people whose ignorance of the cultivated language has led to their adoption of peculiarities sanctioned by no grammatical rule; or, on the other hand, these peculiarities may partake rather of the character of dialectic differences, and enter more deeply into the organization of the language, and thus may have characterized it from that remoter period, when geographical separation and political isolation may have led to the formation, in the Highlands of Scotland, of a dialectic variety of the common language.

The first is the view taken by Irish grammarians, and if correct, these differences cannot be considered as of any philological importance. The question has not, however, been treated by them in a candid spirit, or with any grasp of the subject; and their opinion must be based upon a more accurate knowledge of the spoken dialect which is the subject of it, and upon a sounder and more impartial examination of those philologic elements which ought to enter into its consideration, before it can be accepted as conclusive. If the second view is the correct one, then it is obvious that the Scotch Gaelic is well deserving of study, as a distinct variety of the Gaelic language which was common to Scotland and Ireland; and everything that tends to throw light upon it, and upon the existence and origin of these differences, acquires a philologic value.

In the study of language, the spoken dialects are of great value. It is from the study of the living dialects, which are not merely corruptions of the spoken language, but present dialectic peculiarities, that we arrive at a full perception of the character and tendencies of the mother tongue.

It is the destiny of all languages, that they no sooner enter upon the domain of history than they begin to alter, decompose, and split into dialects. The formation of the mother tongue belongs to the prehistoric period; and it is a process which, carried on in the infancy and growth of the social state, is concealed from observation. When its possessors first emerge into view, and take their place among the history of nations, counter influences have already been at work, their language has already entered upon its downward course, and we can only watch it in its process of decomposition and alteration, and reach its primitive condition, through the medium of its dialects.

There are two opposing influences by which all languages are affected—the etymologic and the phonetic. The etymologic principle is all-powerful in the formation and original structure of the language, producing combinations of sounds demanded by the laws of its composition, but irrespective altogether of the requirements of harmony, or the tendencies of the human organs of sound. It contains in it, however, the seeds of its own destruction, and has no sooner completed its work of formation than a process of modification and decomposition commences, caused by the respective idiosyncrasies of its speakers, their craving after harmony of combination and ease of utterance, and the influence of physical situation and surrounding agents upon the organs of speech.