120 insrouY of 



with water, and coming to be condensed by the evening's cold, is 

 driven against the tops of the mountains, where being condensed 

 and collected, it trickles down by the sides, into the cavities of 

 the earth ; and running for a while underground, bubbles up in 

 fountains upon the plain. This having made but a short circu- 

 lation, has generally had no long time to dissolve or imbibe any 

 foreign substances by the way.* 



• The cause of springs is, that the water which falls on the surface of the 

 earth, in rain, snow, &e. penetrates its substance till it meets with a stratum 

 of clay, stone, or some otlier matter which stops its descent; it then glides 

 laterally on the stratum which sustains it, and in the direction to « hich it 

 leans, till meeting with an aperture, it appears on tlie surface of the earth iii 

 the form of a spring. As water always has a tendency to descend, springs 

 Hte always lower tlian the source from which they are supplied :— Springs 

 ai-e most common on the sides and at the bottom of mountains ; they are 

 BPldom found quite at the summit of a mountain, and are rare where acoun- 

 try is every where level to a considerable distance, because there the strata 

 are parallel, and do not coudtK-t the water to any particular point. In order 

 to obtain water therefore in flat countries, it is in general necessary to dig 

 Into the earth, where it is found to flow copiously from the sides of the open- 

 ing, at no great distance from the surface. When wells are dug in elevated 

 Kituationa, water is seldom met with till we have dug to a considerable depth, 

 and got below the general level of the country. 



There are some springs which exhibit a very curious phenomenon, a kind 

 of tide or intermission by which the water at certain periods appears to rise a 

 considerable height, and gradually to subside. Tliese are called IntermitUng 

 Springs. Others have a periodical swell, and discharge a greater quantity 

 of water at one time than at another, the changes taking place at equal inter- 

 vals. These are called Reciprocating Springs. It was long imagined that 

 these fountains were replenished by some connection with the sea; that the 

 water was freshened by its progress througli sand and earth, and their rising 

 and falling depended on the tide. It was, however, found, that the periods 

 of the water rising and falling in these springs, did not correspond in point 

 of time with the tides of the adjacent seas, and that the periods were dif- 

 ferent in difterent springs, contrary to the regular rising and falling of the 

 tides of the ocean. The phenomenon has since been satisfactorily explained 

 The first of these kind of springs is very easily accounted for, by supposing 

 the channel which carries the water off from a cavern to have the form of a 

 siph on. In this case the water wUl only flow when it rises in the cavern to a 

 height equal to that of the upper curve of the siphon-formed canal, and it will 

 fill again wnen it descends below it. The following explanation of the second 

 kind of intermitting springs was suggested about a century back by Dr At- 

 well, of Oxford, by attending to the p'.ienomena of Lay well spring, at Brixam, 

 n.ar Torbay, in Devcmsliire. Let A A (plate iii. fig. 4.) be a large cavern 

 near the tup of a hill, which derives its supply of water from the rains or 

 melted snow filtering through the crevices of the mountains ; and let CC re- 

 present the small channel which conveys the waters of the cavern to the 

 ■■■>'>niu.; G in the hill, wiioe they are discharged iu thefurmof aimall epririi;. 



