Page:Voyage in search of La Perouse, volume 1 (Stockdale).djvu/125

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Jan.]
OF LA PEROUSE.
115

into Falſe Bay, it can only happen in conſequence of their having ſurmounted this obſtacle which oppoſes them at the ſouthern extremity of Africa. The dilatation of the lower column of air is ſo much impeded by the compreſſion which it ſuffers, in its aſcent towards the ſummit of this ridge, from the weight of the ſuperincumbent column, that, whenever it has paſſed theſe heights, the reaction of its elaſticity is proportionate to the diminution of the reſiſtance before oppoſed to its expanſion. Its impetuoſity is then ſuch as frequently to looſen ſhips lying in the road from their anchors, and ſet them adrift.

The violence of theſe winds is the greateſt where they deſcend along the declivity of theſe mountains: in the interior of the country ſituated at a ſmall diſtance to the eaſtward, on the contrary, they are very moderate; as I have had occaſion to remark in ſeveral excurſions which I made from the town.

The clouds, with which the ſummit of the ridge is at ſuch times covered, are naturally produced from the enormous maſs of air, which, after becoming ſurcharged with moiſture during its paſſage over a vaſt extent of ocean, when it aſcends into the higher regions of the atmoſphere, depoſits, in the form of clouds, the ſuperabundant water which, on account of the change of

temperature,