THERMAL SPRINGS. 187 



The breaking out of springs, effected by multifarious 

 causes of pressure and by the communication of fissures 

 containing water, is such a universal phenomenon of the 

 surface 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 

 numerous results were collected by Leopold von Buch, 

 Wahlenberg 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. lat. to 71 N. 33 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 34 some very ingenious 



the want of hot sandy tracts upon the banks), see my river voyage, in 

 the Relation Historique, t. ii, pp. 463 and 509. In the Rio Guanca- 

 bamba or Chamaya, which falls into the Amazon, near the Pongo de 

 Rentema, I found the temperature of the water to be only 67.6, as its 

 waters come with prodigious swiftness from the elevated lake Sirni- 

 cocha on the Cordillera. On my voyage of 52 days up the river Mag- 

 dalena, from Mahates to Honda, I perceived most distinctly, from 

 numerous observations, that a rise in the level of the water was indi- 

 cated for hours previously by a diminution of the temperature of the 

 river. The refrigeration of the stream occurred before the cold moun- 

 tain waters from the Paramos near the source came down. Heat and 

 water move, so to speak, in opposite directions and with very unequal 

 velocities. When the water near Badillas 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 dis- 

 co veiy of a prognostic of the approaching rise (the avenida) is of some 

 importance. 



33 Leopold von Buch, Physicalisclie BescJireibung der canarischen 

 Inseln, s. 8 : Poggend. Annalen, Bd. xii, s. 403 ; Bibliotheque Britan- 

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

 Glim, in Helvetia Septentrionali Observatis, pp. 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'Arcucil, t. iii (1817) 

 p. 599. 



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

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



