APPENDIX TO MEMOIR OF PELTIER. 201 



The same fact is observed, if we compare together Berg-en and Stockholm. 

 Bergen is in 60° 23' north latitude, and west of the Scandinavian Alps ; Stock- 

 holm is in 59° 20', and east of that chain of mountains. Bergen is therefore one 

 degree further north than Stockholm, and yet the mean temperature of winter 

 at Bergen is + 0°.79, while at Stockhohn it is — 3°.61, a ditlerence of 4°.4. Besides 

 this, the quantity of water ^\■'llich falls in a _year at Bergen is enormous ; it reaches 

 2,250 millimetres, and in winter 598. At Stockholm, on the other hand, the 

 quantity of water which falls in the year is hut about 520 millimetres, and the 

 fall in Avinter 76. In the latter place, then, there falls in winter about eight 

 times less of water than at Bergen. Moreover, if the total quantity of rain fall- 

 ing in a year be represented by 100, it will be seen that at Bergen there falls in 

 winter 26.6, while at Stockholm there falls but 14.8. These two places, there- 

 fore, fully confirm the facts which we have above indicated, and lend their sup- 

 port to the explanation which we have given. 



Hydrometeors inllnence also the moan temperature of summer; in general, 

 when we penetrate into the interior of Europe, pursuing always the same line of 

 latitude, the mean temperature of summer will be found progressively growing 

 higher ; the difference, however, being not so great as for the winter, and in the 

 inverse direction. This is generally attributed to the fact that on the borders 

 of the ocean there are frequent sea mists which veil the sun. Thus the coun- 

 tries situated near the western coast of Europe have summers somewhat less hot 

 and winters rather less cold than the countries situated in the interior of the con- 

 tinent in the same latitude. Hence the climates have been distinguished as 

 equal or marine climates, and continental or excessive climates. 



If the explanation which we have given of the inclination of the isothennal 

 lines towards the equator in the interior of the continent be true, it is evident 

 that the isochimenal lines {i(t<><; equal, /ecrxajv winter) should, for a certain extent 

 of their com'se, be perpendicular, or nearly so, to the direction of the southwest 

 wind — that is to say, to the direction of the wind pre-eminently a rainy one. 

 Now this is in reality the case. The number of observations is not yet suffi- 

 ciently great to enable us to trace these curves with exactness ; but they .suffice 

 to show the general direction of several of them. If we take, for instance, the 

 localities at which the mean temperature of winter varies between — 1° and 

 — 1° 5, we find that this isochimenal line passes successively by Odessa, Dant- 

 wig, Lund in Denmark and Ullensvang in Norway. This curve extends, 

 therefore, in latitude from 46° 28 to 60° 20 ; it thus traverses 14 degrees of lati- 

 tude and is almost perfectly perpendicular to the direction of the southwest wind. 

 The same is very nearly the case with other isochimenal curves ; the\^ all decline 

 strongly towards the south in proportion as they withdraw from the western coast 

 of Europe in advancing castwardly into the interior of the continent. 



It may be proper in addition to cite Venice, Paris, and Edinburgh ; the first is 

 situated in 45° 26 of latitude, the second in 48° 50, the third in 55° 57. Now, in 

 these three cities the mean temperature of winter is very nearly the same; at 

 Venice and Paris it is -f 3° 3, and at Edinburgh -f 3° 6. 



Sometimes, as the sequel of abundant rains, and especially tempestuous rains, 

 a decided lowering of the temperature is observed. This fact, at first glance, 

 seems in contradiction with the theory of isothermal curves which we have pro- 

 pounded ; yet it is by no means so. Almost always after a storm the sky grows 

 clear, if only for a few hours ; the air of the middle and interior regions, unbur- 

 dened of the great masses of vapor which have been precipitated in the form of 

 rain, then presents a certain degree of relative dryness ; tiie earth, on the con- 

 trary, is soaked with rain; there takes place, therelbre, at its surface an extremely 

 abundant evaporation, which withdraws in a few instants a considerable quan- 

 tity of heat from the earth and the air in contact with it. It is this subtraction 

 of caloric which produces the cold in question. 



The temperature indicated by the thermometer, moreover, is not always in accord* 



