180 COSMOS. 



The breaking out of springs, effected by multifarious 

 causes of pressure and by the communication of fissures con- 

 taining water, is such a universal phenomenon of the sur- 

 face of the earth, that waters flow forth at some points from 

 the most elevated mountain strata, and at others from the 

 bottom of the sea. In the first quarter of this century nu- 

 merous results were collected by Leopold von Buch, Wahlen- 

 berg, and myself, with regard to the temperature of springs 

 and the diffusion of heat in the interior of the earth in 

 both hemispheres, from 12 S. latitude to 71 N.* The 

 springs which have an unchangeable temperature were care- 

 fully separated from those which vary with the seasons ; 

 and Leopold von Buch ascertained the powerful influence of 

 the distribution of rain in the course of the year ; that is 

 to say, the influence of the proportion between the relative 

 abundance of winter and summer rain upon the temperature 

 of the variable springs, which, as regards number, are the 

 most widely distributed. More recently! some very ingen- 



velocities. When the water nearBadillas rose suddenly, the tempera- 

 ture fell long before from 80'6 to 74 -3. As, during the night, when 

 one is established upon a low sandy islet, or upon the bank, with bag 

 and baggage, a rapid rise of the river may be dangerous, the discov- 

 ery of a prognostic of the approaching rise (the avenida) is of some 

 importance. 



* Leopold von Buch, Physicalische Beschreibung der canarischen In- 

 seln, s. 8 ; Poggendorf, Annalen, bd. xii., s. 403 ; BibliotJieque Britan- 

 nique, Sciences et Arts, t. xix., 1802, p. 263 ; Wahlenberg, De Veget. et 

 dim. in Helvetia, Septentrionali Observatis, p. Ixxviii. and Ixxxiv. ; 

 Wahlenberg, Flora Carpathica, p. xciv., and in Gilbert's Annalen, bd. 

 xli., s. 115 ; Humboldt, in the Mem. de la Soc. d 1 Arcueil, t. iii. (1817), 

 p. 599. 



t De Gasparin, in the Bibliotheque Univ. Sciences et Arts, t. xxxviii., 

 1828, p. 54, 113, and 264; Mem de la Soc. Centrale d' Agriculture, 

 1826, p. 178 ; Schouw, Tableau du Clirnat et de la Vegetation de I'ltalie, 

 vol. i., 1839, p. 133-195 ; Thurmann, Sur la temperature des sources de 

 la chaine du Jura, comparee d celle des sources de la plaine Sitisse, des 

 Alpes et des Vosges, in the Annuaire Metcorologique de la France, 3 850, 

 p. 258-268. As regards the frequency of the summer and autumn 

 rains, De Gasparin divides Europe into two strongly-contrasted regions. 

 Valuable materials are contained in Kamtz, Lehrbucli der Meteorologie, 

 bd. i., s. 448-506. According to Dove (Poggend., Annalen, bd. xxxv., s. 

 376) in Italy, " at places to the north of which a chain of mountains 

 is situated, the maxima of the curves of monthly quantities of rain 

 fall in March and September ; and where the mountains lie to the 

 south, in April and October." The totality of the proportions of rain 

 in the temperate zones may be comprehended under the following 

 general point of view : " The period of winter rain in the borders of 

 the tropics constantly divides, the farther we depart from these, into 

 two maxima united by slighter falls, and these again unite into a 



