28 



through their sides, either in perpetual or intermitting 

 currents. 



With regard to the first, it has been shewn, that every 

 ten square inches of the surface of the sea, yields a N 

 square inch of water daily; every square mile 6^14 

 tons: and pursuing the same proportion, every square 

 degree (or sixty.nine English miles,) will yield 33 

 millions of tons. Now if we suppose the Mediter- 

 ranean tofhe 40 degrees long, and 4 broad, at a medium, 

 (which is the least we can suppose) its surface will be 

 IfjO square degrees : from whence there will in summer 

 evaporate daily 5280 millions of tons. 



The Mediterranean receives water, (to say nothing of 

 small and inconsiderable streams) from eight large 

 rivers, the Tberus, the Rhine, the Po, the Danube, the 

 Neister, the Borysthenes, the Tanais, and the Nile. Now 

 suppose each of these conveys ten times as much water to 

 the sea as the Thames. The Thames has been shewn to 

 pour daily into the sea 203 millions of tons. Therefore 

 all those rivers will produce 1827 millions of tons. But 

 this is little more than one third of the quantity daily 

 evaporated from the sea. How prodigious a quantity 

 then remains for rains and all other purposes! 



Let us observe, secondly, how the mountains arrest, 

 and collect these vapours, and then discharge them in 

 springs. 



The tops of mountains in general abound with ine- 

 qualities, cavities, grottos, and gaping cells. The floating 

 vapours are stopt by these and by their pointed summits, ' 

 and being condensed thereby, precipitate in water, easily 

 penetrate through sand and lighter earth, and gather in 

 basons of clay or stone, till they overflow and work a 

 passage through the side of the mountain. 



And yet we need not deny, that some springs may 

 arise from the sea, or the gr r eat abyss : those in par- 

 ticular, which at all times afford the same quantity of 

 water. Some of these are found in almost every 

 country. There is one near Upminster, in Essex; which 

 in the greatest droughts, and when all the brooks are 



