CLIMATOLOGY. 323 



Even in the Faroe Islands, at 62° latitude, the inland waters 

 never freeze, owing to the favoring influence of the west winds 

 and of the sea. On the charming coasts of Devonshire, near 

 Salcomhe Bay, which has been termed, on account of the 

 mildness of its climate, the Mont-pellier of the Nwth, the 

 Agave Mexicana has been seen to blossom in the open air, 

 while orange-trees trained against espaliers, and only slightly 

 protected by matting, are found to bear fruit. There, as well 

 as at Penzance and Gosport, and at Cherbourg on the coast 

 of Normandy, the mean winter temperature exceeds 42°, fall- 

 ing short by only 2^*4 of the mean winter temperature of 

 Montpellier and Florence.* These observations will suffice 

 to show the important influence exercised on vegetation and 

 agriculture, on the cultivation of fruit, and on the comfort of 

 mankind, by differences in the distribution of the same mean 

 annual temperature, through the different seasons of the year. 

 The lines which I have termed isochimenal and isotheral 

 (lines of equal winter and equal summer temperature) are by 

 no means parallel with the isothermal lines (lines of equal 

 annual temperature). If, for instance, in countries where 

 myrtles grow wild, and the earth does not remain covered 

 with snow in the winter, the temperature of the summer and 

 autumn is barely sufficient to bring apples to perfect ripeness, 

 and if, again, we observe that the grape rarely attains the 

 ripeness necessary to convert it into wine, either in islands or 

 in the vicinity of the sea, even when cultivated on a western 

 coast, the reason must not be sought only in the low degree 

 of summer heat, indicated, in littoral situations, by the ther- 

 mometer when suspended in the shade, but likewise in another 

 cause that has not hitherto been sufficiently considered, al- 

 though it exercises an active influence on many other phe- 

 nomena (as, for instance, in the inflammation of a mixture of 

 chlorine and hydrogen), namely, the difference between direct 

 and diffused light, or that which prevails when the sky is clear 

 and when it is overcast by mist. I long since endeavored to 

 attract the attention of physicists and physiologistsf to this 



* Humboldt, Sur lea Lignes Isothermes, in the Mimoires de Physique 

 n de Chimie de la SocUti d^Arcueil, t. iii., Paris, 1817, p. 143-165 ; 

 Knight, in the Transactions of the Horticultural Society of London, vol. 

 , p. 32 ; Watson, Remarks on the Geographical Distribution of British 

 Plants, 183.5, p. 60 ; Trevelyan, in Jamieson's Edinburgh New Phil. 

 Journal, No. 18, p. 154; Mahlraann, in his admirable German transla 

 lion of my Asie Centrals, th. ii., s. 60. 



t " Hicc de tem[)etie aeris, qui terram late circumfundit, ac in quo, 

 loiige a solo, instminenta nostra raeleorologica suspensa habemus. Sed 



