Imatges de pÓgina
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than is believed, and which may be derived from the strata containing animal fossil remains, through which the spring waters percolate, ought to be looked for, because its presence will afford to the chemist an opportunity of examining a substance of a very curious nature; to the geologist, data for interesting speculation; and to the physician the means of judging of the mode of action of those waters containing it, in scrofula and other diseases in which its use is said to be so beneficial. It may happen here, as in other countries, that the springs deposite around their sources, and at greater or less distances from them, much of the dissolved and suspended foreign matter they contained, and thus give rise to mineral formations, the external aspect and mode of arrangement of which will illustrate geological phenomena observed among the older rock-formations of which the crust of the earth is composed. Lastly, when it is known that hot springs are intimately connected with subterranean igneous agency,-that power which formerly acted so extensively in forming and modifying the rocks of which the crust of the earth is composed, and which even now continues, although on a less extensive scale, to occasion considerable changes on the surface of the earth, -their natural and chemical history becomes very interesting from the light they shed over many important geological phenomena.

Geology of Caffraria, Natal, &c.-The geology of the countries of Caffraria and Natal is entirely unknown. In Sofala there are said to be mines of silver; and gold is collected from the sands and gravels of some districts. The kingdom of Monomotapa, as it is called, at the distance inland of

about forty days' journey from Sofala, affords gold, topazes, and rubies. The geology of the country from Delagoa Bay, in lat. 26° S., to Cape Delgado, in lat. 10° S., is unknown; a small quantity of golddust is collected in it. From Cape Delgado to the equator, the country, which is under the dominion of the Imam of Mascat, is unknown in a geological point of view. The country from the equator to the Straits of Babelmandeb has never been visited by any geologist.

CONCLUSION.

From the preceding details it results,

1. That, of all the quarters of the globe, Africa has the most truly tropical climate.

2. That, notwithstanding its nearly insular form, its extent of coast is much less in proportion to its area than in the other quarters of the globe.

3. That the peculiar condition of the human species, the distribution and even the aspect of the lower animals and plants, and many of the characters of the African climate, are connected with its comparatively limited extent of sea-coast, its extensive deserts, and arid soil.

4. That from the maritime situation of Sierra Leone and its colonization by Britain, and the connexion of the southern parts of the Great TableLand with the British settlements on the southern coasts of Africa, we may conjecture that the civilization of the negroes (if that interesting race be not destined to extirpation, as has been the fate of the aborigines of the New World,) will be effected from these two quarters, through the energy, enterprise, and perseverance of missionaries, well in

structed in the various useful arts of life, and in the simple and pure principles of Christianity.

5. That its springs, lakes, rivers, bays, and arms of the sea, are fewer in number, and present more uniformity of aspect than is generally the case in other parts of the world.

6. That it is eminently characterized by its vast central and sandy deserts, its great southern tableland, and the vast expanses of Karroo ground.

7. That, of all the rock-formations, those of limestone and sandstone are the most frequent and most widely distributed: that natron, a rare deposite in other countries, is comparatively abundant in Africa; that salt is very widely distributed, though in some districts it is wholly deficient; but coal is wanting. And the precious stones, so frequent in other tropical regions, are here of rare occurrence.

8. That the metals, although met with in different quarters, are nowhere abundant; and that, of all the different metals, gold is the most generally distributed.

9. That no active or extinct volcanoes have hitherto been met with.

10. Lastly, That Africa is less frequently agitated by earthquakes than the other continents.

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