200 APPENDIX TO MEMOIR OF PELTIER. 



For furtlier details ou this subject recourse may be had to the great treatise on 

 meteorology of Kaemtz, in 3 volumes, pp. 450, 500 ; the smaller treatise on 

 meteorology by the same author, translated, with notes by Ch. Martins, p. 138 

 and seq.; the memoirs of Gasparin on the distribution of rains in Europe, 

 fBihliotheque UnkcrseUe, t. 38, pp. 54 and 264 ;) and the Atlas PJii/siqfte of 

 Bergliaus, charts 10 and 12 of the meteorology, p. 19 and seq. of the test. 



The tables above given establish, therefore, the three facts in question : the 

 diminution of temperature, the diminution of the annual quantity of water, and 

 the diminution of the relative quantity of water falling in winter. What, now, 

 is the cause of these three phenomena ? what is the Ijond which connects them ? 

 It is this which we propose to explain while expressing ourselves with all the 

 reserve which is proper on such a subject. 



The winds of the southwest bear from the Atlantic ocean a large quantity of 

 clouds and vapors ; these, nearly throughout Europe, are the winds pre-emi- 

 nently rain3% The clouds are formed of globules of transparent vapor and of 

 globules of opaque vapor, b(jth kept apart by the latent caloric and the elec- 

 tricity, which render them mutually repellant. If any cause abstracts from a 

 cloud the greater part of its electricity, one of the two forces which co-operated 

 to keep the globules separate is suppressed. The globules of transparent vapor 

 approach one another, are condensed, and transfomied into opaque vapors ; the 

 glol)ules of opaque vapor, for the same reason, pass into a liquid state, the dens- 

 ity of the cloud, its specific gravity, is augmented, the cloud sinks and falls on 

 the earth in the form of rain. On arriving at the surface the cloud disengages 

 the latent heat it possessed, and thus the soil, as well as the ambient air, is ren- 

 dered warm. 



The quantity of rain which falls annually is naturally, all else being equal, 

 more abundant in western Emope than in the interior of that continent; the 

 forests, the mountains, especially when wooded, radiate much electricity ; they 

 neutralize, therefore, the electricity of the clouds, and thus induce, in a manner 

 more or less indirect, their precipitation. When this cun-ent from the switliwest 

 reaches Germany it is already deprived of a great part of its vapors. When it 

 arrives in Russia, there remains still less of them ; finally, in Siberia there is 

 scarcely any at all remaining. It thus appears that the quantity of water which 

 falls in a year must continue always diminishing as we penetrate into the interior 

 of the continent ; it is evident, consequently, that the quantity of latent heat 

 abandoned by the clouds must also progressively diminish, and that the tempera- 

 ture must undergo a corresponding abatement. These facts are more marked in 

 winter than at any other season, because then the wind from the southwest brings 

 a less quantity of vapors, while these are less elevated and consequently termi- 

 nate at lower latitudes. Another cause, moreover, coucm-s in augmenting the 

 asperity of the cold in the interior of Eussia : this is the intensity of the radia- 

 tion which takes place in consequence of the great serenity of a sky which is 

 obscured by neither cloud nor vapor. 



It results from what has been just said, that a locality in Europe situated to 

 the east of a chain of mountains should always be colder, all else being equal, 

 than a locality situated to the west. The chain of mountains in effect, by pre- 

 cipitating a great quantity of vapors, must have abstracted a considerable por- 

 tion of the latent heat, which is hence naturally in deficiency on the other side ; 

 moreover, if these places are 'situated in a latitude somewhat high, where the 

 clouds are akeady very low, this effect will be still more decided. This in 

 reality is what occurs as respects Sweden and Norway in reference to the Scan- 

 dinavian Alps. We may cite as an example Drontheim in Norway, and Umeo 

 on the Gulf of Bothnia, in Sweden, (see VlnstiUd of 18th February, 1846, p 61, 

 the connnunication of M. Martins.) These two cities are nearly in the same 

 latitudes and yet the mean temperature of Drontheim during winter is — 4°. 75^ 

 while that of *Umeo is— 10°.2, a difference of 5°.45. 



