THE EARTH. 141 



and many of these uniting, make such vast bodies of water as 

 the Rhine, the Rhone, and the Danube. 



There is still a third part which falls upon the lower grounds, 

 and furnishes plants with their wonted supply. But the cir- 

 culation does not rest even here ; for it is again exhaled into va- 

 pour by the action of the sun ; and afterwards returned to that 

 great mass of waters whence it first arose. " This," adds Dr 

 Halley, " seems the most reasonable hypothesis ; and much more 

 likely to be true, than that of those who derive all springs from 

 the filtering of the sea-waters, through certain imaginary tubes 

 or passa-ges within the earth ; since it is well known that the 

 greatest rivers have their most copious fountains the most re- 

 mote from the sea.'" 



This seems the most general opinion ; and yet, after all, 

 it is stUl pressed with great difficulties ; and there is still room 

 to look out for a better theory. The perpetuity of many springs, 

 which always yield the same quantity, when the least rain or va- 

 pour is afforded, as well as when the greatest, is a strong objec- 

 tion. Derham^ mentions a spring at Upminster, which he 

 could never perceive by his eye to be diminished, in the greatest 

 droughts, even when all the ponds in the country, as well as an 

 adjoining brook, have been dry for several months together. In 

 the rainy seasons, also, it was never overflowed ; except some- 

 times, perhaps, for an hour or so, upon the immission of the ex- 

 ternal rains. He, therefore, justly enough concludes, that had 

 this spring its origin from rain or vapour, there would be found 

 an increase or decrease of its water, corresponding to the causes 

 of its production. 



Thus the reader, after having been tossed from one h}'j)othe- 

 sis to another, must at last be content to settle in conscioue 

 ignorance. All that has- been written upon this subject, 

 affords him rather something to say. than somettiing to think ; 

 something rather for others than for himself. Varenius, 

 indeed, although he is at a loss for the origin of rivers, is by no 

 means so as to their formation. He is pretty positive that all 

 rivers are artificial. He boldly asserts that their channels have 

 been originally formed by the industry of nian. His reasons 

 are, that when a new spring breaks forth, the water does not 



J Pliil. Trans. v.;l. ii. p. 128. 2 DirihamPIiysico-Theol, 



