On the Geology of some parts of Madeira

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Abstract
D uring a stay of two months in Madeira, Sir C. Lyell had an opportunity of examining a considerable portion of the island, and extracts from his letters to Mr. L. Horner, read at this evening's meeting, contained observations on the geological structure of Madeira and the neighbouring islands of Porto Santo and Baxo. In nearly all his excursions. Sir Charles was favoured by the company of Mr. Hartung, a German naturalist resident at Funchal, who proved a most active fellow-labourer. Sir Charles agrees with Mr. Smith, of Jordan-hill, in attributing a subaërial origin to the great mass of the volcanic rocks of Madeira. Some of the earlier igneous formations were submarine, and are associated at San Vincente, in the northern part of the island, with deposits containing corals and sea-shells. These marine strata are elevated at least 1200 feet above the sea. A long and complicated series of volcanic eruptions, for the most part subsequent in date to the above, and which took place in the open alr, built up the island. They have given rise to a mountain-chain about thirty miles in length, running east and west. This chain in its middle and loftiest portion rises to the height of 5000, and in some peaks to more than 6000 feet. Its composition is displayed in the precipitous sides of valleys more than 3000 feet deep, and is seen to consist entirely of scoriae, lapilli, breccias with angular fragments of volcanic rocks, tuft, scoriaceous lava, and some beds of solid

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