176 Mayow 



depths of the sea ? For it is by no means to be 

 beheved that sea-water ascends by filtration to the 

 tops of mountains ; for in whatever way any liquid 

 may rise up through a filter, yet it will not flow out 

 of the filter unless its other end is at a lower level 

 than the liquid ; and consequently sea-water obviously 

 cannot gush out by means of filtration from places at 

 a higher level than the ocean itself. 



Whether sea-water, which, in consequence of being 

 impregnated with salt, is heavier than spring-water, 

 is comparatively so much heavier as to force 

 spring-water to the tops of lofty mountains, as the 

 ingenious Dr R. Hooke has suggested, I will not 

 definitely say ; yet it can scarcely be thought that any 

 springs are due to this cause. For if any had their 

 source in the sea, how are we to explain that most 

 fountains follow the temperature of the air and almost 

 fail in very warm weather, or also in frost ? Should 

 any one say that the aqueous particles are by reason 

 of the greater heat converted into vapours and ascend, 

 and that therefore the springs dry up in summer, I 

 ask, how is it then that fountains are diminished when 

 the earth outside is so bound by frost that the passage 

 for vapours is entirely closed ? 



I think, then, that it should be held that at least the 

 majority of springs have their origin in rain-water. 

 And yet I would not be understood as supposing that 

 rain-water is stored in certain subterranean caverns, 

 as it were in special cisterns, whence it flows out into 

 springs. For such a supposition is unnecessary when 

 the thing can be otherwise explained. Now since 

 the surface of the earth is like a sponge or filter, it can 

 absorb rain-water in quantity suflScient to form 

 springs that will endure for a long time. For we 

 observe that the outer crust of the earth is always 



