THE EARTH. 



CHAPTER XIV. 



OF THE ORIGIN OF RIVERS. 



" THE sun ariseth, and the sun goeth down, 

 and pants for the place from whence he 

 arose. All things are filled with labour, and 

 man cannot utter it. All rivers run into the sea, 

 yet the sea is not full. Unto the place whence 

 the rivers come, thither they return again. 

 The eye is not satisfied with seeing, nor the 

 ear with hearing.'" Thus speaks the wisest 

 of the Jews. And at so early a period was 

 the curiosity of man employed in observing 

 these great circulations of nature. Every eye 

 attempted to explain those appearances; and 

 every philosopher who has long thought up- 

 on the subject, seems to give a peculiar solu- 

 tion. The inquiry whence rivers are produ- 

 ced ; whence they derive those unceasing 

 stores of water, which continually enrich the 

 world with fertility and verdure ; has been 

 variously considered, and divided the opin- 

 ions of mankind more than any other topic 

 in natural history. 



In this contest the various champions may 

 be classed under two leaders ; Mr. De la 

 Hire, who contends that rivers must be sup- 

 plied from the sea, strained through the pores 

 of the earth ; and Dr. Halley, who has endea- 

 voured to demonstrate that the clouds alone 

 are sufficient for the supply. Both sides 

 have brought in mathematics to their aid ; 

 and have shown that long and laborious cal- 

 culations can at any time be made to obscure 

 both sides of a question. 



De la Hire b begins his proofs, that rain- 

 water, evaporated from the sea, is insufficient 

 for the production of rivers; by showing that 

 rain never penetrates the surface of the earth 

 above sixteen inches. From thence he infers, 

 that it is impossible for it, in many cases, to 

 sink so as to be found at such considerable 

 depths below. Rain-water, he grants, is often 

 Been to mix with rivers, and to swell their 

 currents ; but a much greater part of it eva- 



a Ecclesiastes, chap. i. ver. 5, J, 8. 

 b Hist, de 1'Acad. 1713, p. 56. 



porates. " In fact," continues he, " if we sup- 

 pose the earth every where covered with 

 water, evaporation alone would be sufficient 

 to carry off two feet nine inches of it in a 

 year: and yet we very well know, that 

 scarcely nineteen inches of rain-water falls 

 in that time ; so that evaporation would car- 

 ry off a much greater quantity than is ever 

 known to descend. The small quantity of 

 rain-water that falls is, therefore, but barely 

 sufficient for the purposes of vegetation. Two 

 leaves of a fig-tree have been found, by ex- 

 periment, to imbibe from the earth, in five 

 hours and a half, two ounces of water. This 

 implies the great quantity of fluid that must 

 be exhausted in the maintenance of one sin- 

 gle plant. Add to this, that the waters of 

 the river Rungis will, by calculation, rise to 

 fifty inches; and the whole country from 

 whence they are supplied!!, ever receives fif- 

 ty inches in the year by rain. Besides this, 

 there are many salt springs, which are known 

 to proceed immediately from the sea, and are 

 subject to its flux and reflux. In short, 

 wherever we dig beneath the surface of the 

 earth, except in a very few instances, water 

 is to be found : and it is by this subterraneous 

 water that springs and rivers, nay, a great 

 part of vegetation itself, is supported. It is 

 this subterraneous water which is raised into 

 steam, by the internal heat of the earth, that 

 feeds plants. It is this subterraneous water 

 that distils through interstices; and there, 

 cooling, forms fountains. It is this, that by 

 the addition of rains, is increased into rivers, 

 and pours plenty over the whole earth." 



On the other side of the question/ it is as- 

 serted, that the vapours which are exhaled 

 from the sea, and driven by the winds upon 

 land, are more than sufficient to supply not 

 only plants with moisture, but also to furnish 

 a sufficiency of water to the greatest rivers. 



c Phil. Trans. voL ii. p. 128. 



