2 78 BBOiATION OF FOEBSTS TO THE 



from North to South, between the walls of the Forez and of the 

 Jura. This basin is crossed by the west wind, which distributes its 

 rain in such a way as to give clear testimony to the influence of 

 mountain elevations. * 



Begions. 



Slope of the Forez passed over by tlie 



pluvial wind descending, 

 Bottom of (Eight bank of the Saone, 



Valley. (Left bank of the Saone, 

 Adjacent region at the base of the Jura 



passed over by the pluvial wind re- 



ascendiag, 301 1087-8 5 „ 



Gorges of the Jura where the pluvial 



current is compressed, 549 1358 -0 8 „ 



" From this table it is seen that the pluvial wind produces very 

 different effects indeed according as it descends an incline, or re- 

 mounts an acclivity. When it is descending it gives quantities of 

 rain almost equal at the very different altitudes of 440 and 252. 

 While, when it re-ascends, it suffices to pass on the opposite bank, from 

 the level of 234 to the height of 301, for the quantity of rainfall to 

 increase 50 per cent. During the descent there is precipitated less 

 rain at the level of 252, than is precipitated in the re-ascent at the 

 lower level of 234 ; there falls twice as much rain on the re- 

 ascending acclivity, at the level of 549 mfetres, than falls on the 

 descending incline by which it came, at the level of 440 mfetres, 

 although the difference between the two altitudes scarcely exceeds 

 100 metres." 



From what has been advanced it may be seen that in rainfall 

 determined by geographical position, the distribution of this is 

 greatly modified by the contour of the country. But this is not 

 done only in the way which has been referred to. M. Cdzanne goes 

 on to say : — " The elevation of the ground acts in yet another way 

 on the distribution of the rain : altitude modifies the proportion of 

 rain falling in the different seasons of the year ; in this way elevation 

 above the level of the sea has the same influence as distance from the 

 coast. During summer the maximum of rain falls in places of con- 

 siderable elevation or distance from the sea, but during winter in 



* L'l^veiUs : Medhferohea, do. 



