Outlines of the geographical distribution of British plants : belonging to the division of vasculares or cotyledones / by Hewett Cottrell Watson.

Date:
[1832?]
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of the geographical distribution of British plants : belonging to the division of vasculares or cotyledones / by Hewett Cottrell Watson. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    first lapses into the second, and the second into the third, in so gradual a nianner, that it is quite iinpossihle to draw any mathematical line of demarcation. These districts, or zones of vegetation and tempera- ture, ai'e by no means correspondent with the latitudi- nal lines of geographers. From the researches and calculations of Humboldt, it appears, that to a certain distance from the Equator, lo or 20°, the mean an- nual temperature is nearly the same in all longitudes, varied somewhat by local circumstances. As we recede from the Equator northward, this equality of tempera- ture in similar latitudes becomes less and less exact, any given parallel on tbe western coasts having a mean temperature considerably higher than is found in the corresponding latitude of the eastern. A comparison of the west of Europe with the opposite or eastern coast of America will make this very apparent. Hum- boldt carries his isothermal lines (lines of equal mean temperature) of 32°, 50°, and 68°, thus :— Temp. W. of Europe. E. of America. Diff. of Lat. O 32 71 N. L. North Cape. O 57 Labrador. O 14 SO 53 J W. of Ireland. 42^ United States. 11 68 32J Madeira. 29^ Florida. 3 For particular details on this highly interesting sub- ject, we must refer to the works of Humboldt, and to the translation of his treatise on Isothermal Lines, in volumes iii. iv. and v. of the Edinburgh Philosophical •Journal. The subject of climate would require vo- lumes rather than pages.
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