To the south of Dolgellau, Cader Idris towers above the subject mountains, which seem to retire, to allow its base more room to stand, and to afford to their sovereign a better display. It stands on a broad rocky base, with a gradual ascent to its brow, when the peaks elevate themselves in a manner at once abrupt, picturesque and distinct. The point emphatically named Cader, appears to the eye below to be little superior in hight to the saddle; but the third point, or apex, which has a name expressive of its sterility, is neither equal in hight, nor in beauty, to the other two. On its loftiest peak a stone pillar has lately been erected, for the purpose of a trigonometrical survey. Cader Idris is the commencement of a chain of primitive mountains, and is computed to be twenty-eight hundred and fifty feet above the green of Dolgellau, and thirty-five hundred and fifty feet, or nearly three-fourths of a mile above the level of the sea. It has been conjectured that at some remote period it was a volcano of immense magnitude. The tract to the south of Cader Idris, as far as Talylyn and Malwydd, is peculiarly grand. High and rugged mountains of every possible form, close in on all sides, while huge masses of rock hang over, or lie scattered in misshapen fragments by the side of the road. To add to the effect of this scene, the river Difi forms one continued cataract for five or six miles, overflowing with the innumerable tributary torrents which precipitate themselves from the highest summits of the surrounding rocks; while, to crown the whole, the shady head of Cader Idris towers, the majestic sentinel of the group. PENMAN-MAWR. The county of Caernarvon, in which this mountain is situated, claims precedency over every other in Wales, for the loftiness of its mountains, and the multitude of the eminences, which in a curved and indented chain, occupy nearly the whole of its extent. In proceeding from Conway to Bangor, by a route at once picturesque and romantic, and amid a scenery which varies at every step, Penman-mawr discloses to the traveler its bulky head. It protrudes itself into the sea, and exhibits a fine contrast to the fertility which it interrupts, by a rude view of gray weather-beaten stones and precipices. The passage over the mountain was formerly terrific; but the road has been latterly widened and secured, near the verge of the precipice, by a small wall about five feet in hight. It forms the most sublime terrace in the British isles, winding round the mountain on the edge of the abrupt cliff; while the vast impending rocks above, the roaring of the waves at a great distance below, and the frequent howling of the wind, all unite to fill the mind with solemnity and awe. SKIDDAW.