362 Professor Fournet's Besearches on the 



The first of the zones in question, that of two annual rainsy 

 having a great tendency to pass into continual rains, is placed 

 nearly at the equator, with the exception of some deviations, 

 which it is unnecessary to specify at present. There then 

 come the bands of hemi-annual rains, comprised between the 

 equinoctial line and the tropics. In these it rains during the 

 six months following the period of the sun's passing the zenith ; 

 that is to say, there are summer rains in the northern hemi- 

 sphere, and winter rains in the southern hemisphere. These 

 semestrial rains degenerate into trimestrial rains near the 

 tropics. This intertropical arrangement is perfectly regulated, 

 so that it may be said, in a general manner, that to absolute 

 dryness, lasting some months, succeed almost daily rains during 

 the other season. In this manner are constituted the seasons 

 of suns and of clouds of the Indian of the Orinocco ; and it is 

 only the presence of high chains of mountains, or the vicinity 

 of coasts, which produces disturbances in the phenomena of 

 this description. 



Without the tropics. Von Buch was the first to point out 

 the existence of zones termed sub-tropical, in which the rains 

 become the reverse of what they were in the bands already 

 mentioned ; that is to say, they are hyemal in our hemisphere, 

 and estival in the southern hemisphere ; in other words, they 

 occur in each of these situations when the sun is in the oppo- 

 site hemisphere, and as examples of this, we may cite Algeria 

 and the Cape of Good Hope. The arrangement here no longer 

 possesses the extreme regularity which characterises that in 

 the tropics ; for sudden falls of rain and storms interrupt from 

 time to time the uniformity of the dryness of other periods of 

 the year, just as the rains are subject to frequent interruptions. 



Further to the north, in our hemisphere, matters become 

 still more complicated by the intercalation of irregular and 

 more frequent rains ; but taking the sums of several years, we 

 find that the months characterised by the largest quantities 

 of pluvial water are those of spring and of autumn ; such is 

 the arrangement which prevails in the whole of the south of 

 Europe, as far as about the latitude of Paris. 



Lastly, beyond this, and towards the North Pole, these rains 

 of spring and of autumn unite so as to produce a maximum in 



