SURFACE OF THE GLOBE. 47 



computed to discharge more water annually than all 

 that falls in the surrounding country; and the same, 

 even to a greater degree, is true of that of the Sorgne 

 in France. It has been imagined that such springs 

 were produced from the sea; hut neither chemistry 

 nor hydrostatics will admit of such deviations from 

 their laws. The hot springs of Bath are still more 

 inexplicable; but it is unnecessary to enumerate all 

 the difficulties of this nature which may be found in 

 the writers who have treated of this curious subject. 

 That it is connected with important geological facts 

 as yet unknown to us, is unquestionable; but it is 

 fruitless to form conjectures, and frivolous to construct 

 hypotheses, as substitutes for knowledge. 



Although considerable streams sometimes arise at 

 once out of the earth from their springs, they are most 

 commonly formed from the collected tribute of the 

 innumerable small rills which, in hilly countries, 

 trickle down the sides of mountains ; on some part or 

 other of which, rain is seldom wanting for many days, 

 or even hours. In summer also, the gradual melting 

 of the snows furnishes those resources which the re- 

 currence of cloudless weather may have intercepted. 

 It is for this reason that all the great rivers of the 

 world have their rise in mountainous countries ; and, 

 for the same reason, extensive plains often present arid 

 tracts unwatered by a single stream. 



In our own country, the Tay arises from sources 

 that may fairly be called innumerable. The Wolga 

 and the Danube are each formed of more than two 

 hundred principal streams. Among those which the 

 Amazon, or Maranon, receives, many are in them- 

 selves large rivers ; and thus, as the length of their 

 courses increase, most of the great rivers of the earth 

 are constantly augmenting their waters till they vanish 



