430 PHILOSOPHICAL TRANSACTIONS. [aNNO ISQO-I. 



night, falls in dews, or else in rains, again into the sea, before it reaches the 

 land, which is by much the greatest part of the whole vapour, because of the 

 great extent of the ocean, which the motion of the winds does not traverse in 

 a very long space of time. And this is the reason why the rivers do not return 

 so much into the Mediterranean as is extracted in vapour. A third part falls on 

 the lower lands, and is the pabulum of plants, where yet it does not rest, but is 

 again exhaled in vapour by the action of the sun, and is either carried by the 

 winds to the sea, to fall in rain or dew there, or else to the mountains, to be 

 there turned into springs ; and though this does not immediately happen, yet 

 after several vicissitudes, of rising in vapour and falling in rain or dews, each 

 particle of the water is at length returned to the sea from whence it came. 

 Add to this, that the rain waters, after the earth is fully sated with moisture, 

 by the valleys or lower parts of the earth finds its way into the rivers, and so is 

 compendiously sent back to the sea. After this manner is the circulation per- 

 formed, and I doubt not but this hypothesis is more reasonable than that of 

 those who derive all springs from the rain waters, which yet are perpetual and 

 without diminution, even when no rain falls for a long space of time ; or than 

 that which derives them from a filtration of the sea waters through certain ima- 

 ginary tubes or passages within the earth, wherein they lose their saltness. 

 This latter hypothesis, besides many others, labours under this principal absur- 

 dity, that the greatest rivers have their most copious fountains farthest from the 

 sea, and whither so great quantities of fresh water cannot reasonably be derived 

 any other way than in vapour. This, if we may allow final causes, seems to 

 be the design of the hills, that their ridges being placed through the midst of 

 the continents, might serve as it were for alembics to distil fresh water for the 

 use of man and beast, and their heights to give a descent to those streams to 

 run gently, like so many veins of the macrocosm, to be the more beneficial to 

 the creation. 



Now this theory of springs is not a bare hypothesis, but founded on experi- 

 ence, which it was my luck to gain in my stay at St. Helena, where in the night 

 time, on the tops of the hills, about 800 yards above the sea, there was so 

 strange a condensation, or rather precipitation of the vapours, that it was a 

 great impediment to my celestial observations ; for in the clear sky the dew 

 would fall so fast as to^cover, each half quarter of an hour, my glasses with little 

 drops, so that I was necessitated to wipe them so often, and my papers on 

 which I wrote my observations would immediately be so wet with the dew, that 

 it would not bear ink. 



