642 PHILOSOPHICAL TRANSACTIONS. [aNNO I79O. 



without any pillars. In some parts of the island the tops of the pillars are 

 standing bare ; in other parts the surface is formed by a rude argillaceous lava, 

 full of bladder-holes, some empty, others replete with quartz crystals. Calca- 

 reous spar, pebbles of indurated clay and shoerl, detached pieces of zeolite, are 

 frequently seen, and the vegetable soil is a decomposed lava. In some places are 

 met with gravel containing pebbles of basaltes, of red granite, and of quartz, 

 their angles worn off, and they were become round and smooth. 



In a small bay, about 1 mile to the s. e. of x\rdlun Head, Loch Lyne, under 

 a bed of jointed lava, which has some resemblance of pillars, and just at high- 

 water mark, is a bed of coal, exactly 12 inches thick, intermixed with shale or 

 bituminous shistus, dipping s. e. towards the loch 1 yard in 3; there is not any 

 intervening substance between the coal and superincumbent lava, which contains 

 many bladder-holes. Beneath the coal is also lava without any intervening matter. 

 About 20 yards to the n. w. the coal again appears in the cliff", but is not more 

 than from 8 to 10 inches thick. Here are tumblers of various sizes, scattered 

 on the shore. Among them are some resembling the Derbyshire toadstone; and 

 a short distance inland, to the s. w., are rude masses of lava, standing up at day, 

 not unlike the great whyn dykes of Hay. In the Loch, and at some distance 

 from the opposite shore, there stood, within the memory of man, an insulated 

 pillar of coal, from which the country people were accustomed to procure a supply 

 for smiths' use; but the quantities they carried away, and the continual washing 

 of the sea, have now entirely removed it. The island of Lismcre, in the sound 

 of Mull, is entirely limestone, excepting where it is crossed by the whyn dykes. 

 In the island of Ulva are pillars somewhat resembling those of Staffa, but of a 

 paler colour. — Canna also is basaltic, and resembles Staffa. — The Dutchman's 

 Cap has rude pillars. — Cairnborough the same. Dunvegan in the isle of Skye 

 has basaltic pillars, similar to Staffa. — On the s. w. side of the isle of Egg is a 

 curious cavern. 



Again embarked for Hay; but, it being calm, and the tide against us, were 

 obliged to anchor; and landed on an island which forms the s. e. point of the 

 sound of lona, which is a bare rock of red granite, broken and jointed in every 

 direction. The upper surface of the granite, even in the very highest part, is 

 all convex, which seems to prove, that by some convulsion it has been thrown 

 up from the bed of the ocean, which, by long washing over it, had previously 

 -worn down its substance at the edges of all its numerous joints. On the east 

 side of the point, and on the west side of a little bay, where the granite cliffs 

 are at least 15 yards perpendicular, discovered a whyn dyke, or vein of lava, 

 about 2 feet wide, included in a vertical fissure ranging s. e. by e. and n. w. by 

 w. About 6 yards to the westward of the lava vein, or whyn dyke, is an im- 

 mense fissure in the granite, ranging n. by w. and s. by e. It is from Q to 10 



