640 PHILOSOPHICAL TRANSACTIONS. [anNO 17Q0. 



time at the mines in the county of Wicklovv, he proceeded to Belfast ; and a 

 little to the northward of that town he discovered in a bank a body of marl, 

 running n. e. and s. w. between red and white sand-stone, the whole included 

 and surmounted by a kind of toad-stone and rude lava, with joints having no 

 particular di"ection. At Belfast he embarked for Hay ; but the wind obliged 

 them to tide along the Irish shore, which, after passing Carrickfergus, chiefly 

 consists of stupendous basalt cliffs. Farther north the cliffs are divided into ho- 

 rizontal beds of considerable thickness, by the intervention of a red substance, 

 similar in appearance to that at the Giant's Causeway ; near the water's edge, 

 and under the lava, the white lime-stone is frequently seen ; and these appear- 

 ances continue all the way to Red Bay. Four miles from Clogh, under a bed 

 of white lime-stone, 40 feet thick, saw the upper part of a bed of gneiss. Sail- 

 ing from hence, plainly saw that the high broken point, which forms the n. e. 

 point of Cushendun Bay, i^ composed of lava, with some rude appearance of 

 pillars near the top ; while close to the water's edge, and at some little distance 

 in the sea, were tumblers of an immense size. 



Entering the sound of lona, saw that the rude coast of Mull, and the less 

 elevated shore of lona, were composed of red granite. At the landing place in 

 loria is laminated horn-stone; and a quarter of a mile north from the ruins of 

 the cathedral is a vein of coarse red granite, 2 feet wide, standing nearly vertical, 

 and ranging with the horn-stone e. n. e. and w. s. w. ; on the surface are tum- 

 blers of red granite, and some few of lava. About a mile n. w. from the 

 cathedral, and near the shore, is a vein, 2 feet wide, containing feld-spath and 

 white mica, ranging e. and w. between granite sides. Many of the rocks are 

 tinged with iron, and there is some bog iron ore in the mosses. In the s. w. part 

 of the island, is a body of white marble, veined with pale green. At the Cove, 

 where it is said St. Columb landed, the cliffs are of red granite, and the shore is 

 covered with great variety of pebbles of serpentine, basaltes, granite, quartz, 

 and other substances. Rowed from Icolmkill through the Bull Sound, which 

 runs between Nun's Island and the island of Mull ; on both sides the cliffs are 

 of red granite, ragged and broken, without any regular beds or fissures, and 

 having no particular range or inclination. Hence steered for Ardlun Head, 

 which forms the s. w. point of Loch Leven, where they contemplated the won- 

 derful arrangement of the basalt columns. 



Near this place is a deep glen, running n. n. e. to the sea. It is about 30 

 yards in length, and 20 in breadth. The strata are disposed in the following ex- 

 traordinary manner. The uppermost is 10 yards of lava, with horizontal divi- 

 sions and vertical joints, taking the form of rude pillars. Under this is an hori- 

 zontal bed of a perfectly vitrified substance, which appears to have been a shale, 

 and is from l to 2 inches in thickness. Beneath this, is about 3 yards of 9 



