A lecture on the geography of plants / By John Barton.

  • John Barton
Date:
1827
Catalogue details

Licence: Public Domain Mark

Credit: A lecture on the geography of plants / By John Barton. Source: Wellcome Collection.

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    lar and striking an aspect,-—we naturally expect to find as marked an increase in the heat of the sun’s rays. This, however, is not the case. There is no reason to believe that the mean temperature at the equator exceeds 82°, a de- gree of warmth by no means very uncommon in our own country. The mean temperature of Cumana, on the northern coast of South Ame- rica, in latitude 10° 27', is 82°; that of Havan- nah, the capital of the island of Cuba, in latitude 23° 10', is 78°; that of Madras, in latitude 13° 5', is 81°; that of Manilla, the principal of the Philippine islands, in latitude 15°, is 78°. In fact, the climate of most parts within the tropics is more remarkable for equability than for ex- treme heat. Twice in the year the sun is ver- tical to every place lying within the torrid zone; therefore every place so situated should have two summers in twelve months, and of course two winters. But, in fact, the difference of temperature at different seasons is so trifling in these regions, as scarcely to attract attention : at Cumana, for instance, the mean temperature of the winter is 80^°; that of thq three hottest months only 83^°. The different seasons are marked by circumstances far more striking than this slight difference of temperature. From the time when the sun becomes vertical in its passage towards the tropic till it again
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