374 Professor Fournet's Besearches on Zones without Bain. 



this arrangement becomes complicated by the winter sub- 

 tropical rains. Thus, at Guadalupe-y-Calvo (lat. 26° 5' N.), 

 independently of the trimestrial estival rains of June, July, 

 and August, which prevail at Mexico, there is a repetition from 

 October till January, during which there are two or three falls 

 of very cold water, continued during several days, and to 

 which the inhabitants of the country give the name of equi- 

 parte. We see, then, here, the reproduction of the phenome- 

 non of Sonora ; so that the hiatus of the Sahara is awanting 

 in this region, and, in fact, meteorology has acquired a know- 

 ledge of various modes of transition from one climate to the 

 other, of which it was ignorant until lately. But these rains 

 do not entirely efface the droughts ; for, according to Von 

 Humboldt, the latter are frightful in a portion of this region, 

 where, moreover, a specimen of a desert is found in the arid 

 and dry plain of Muerto, the extent of which is about thirty 

 leagues ; the dews which are so abundant in Sonora do not 

 exist on those heights. At Chiahuahua, in 25" N., the seasons 

 are still less marked by irregular rains ; and, the atmosphere 

 is so destitute of aqueous vapour, that, at night, during a 

 bivouac, the mere touching one's coverings is sufficient to pro- 

 duce electric sparks, and a Leyden jar can be charged in this 

 manner. 



On the eastern side, Xalappa (lat. 20° N.), at the height of 

 the tierras templadas (temperate regions), is frequently en- 

 veloped in fogs, and there are frequent rains there at all sea- 

 sons; but from Stander to Monterey, from 23° to 26°, and on 

 the banks of the Rio-Bravo-del-Norte, as far as Texas, we 

 immediately find, as in Algeria, the winter rains characterised 

 by small falls of snow, and by the north wind. In this last 

 country, where there are vast savannahs, they are accompanied 

 by frightful storms, while, in the first, there are some summer 

 rains. From this there result transitions analogous to the pre- 

 ceding ; but the warm waters of the gulf, as well as the coast 

 of the Atlantic, increase the various causes of anomalies ; for, 

 at New Orleans, in lat. 29° 27', rains fall during the whole 

 year, although the most violent are in summer ; whereas, at 

 Hey west, the most southern town of the United States in 25° 



