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THE POPULAR SCIENCE MONTHLY. 



got to that higher point. This can best be done by the force demon- 

 strated," etc. But sujjposing, if you can suppose, that a particular over- 

 flowing spring were caused by Mr. Green's " newly discovered force " 

 acting on a lower body of water, it would still be for him to show how, 

 according to his theory, the water got to that lower point. His po- 

 sition plainly is (see p. 81), that if any openings exist between bodies 

 of water imprisoned in the earth's crust and the surface of the earth, 

 these waters, unless entirely isolated bodies, would as a rule flow up- 

 ward. If there were millions of cubic miles of water in accessible sub- 

 terranean i-eservoirs, and no drain on them but that caused by the wells 

 made by man, the supply might be considered " ample for all practical 

 purposes," no matter how it got thei-e or what forced the water up ; 

 but Mr. Green argues that not only flowing springs but the bulk of the 

 waters of the rivers St. Lawrence, " Ganges, Nile, Indus, Senegal, 

 Rhine, Rhone, Vistula, Elbe, Loire, Gaudiana, Po, Adige, Swale, Tay, 

 Severn, Don, Monongahela, Platte, Missouri, and numerous others" 

 must be derived from a subterranean water-supply, which, he says 

 (p. 77), "is known to be constant, and has always been so." One 

 would think that rivers like those mentioned, flowing for centuries, if 

 fed by a subterranean loater-siipply, would ultimately make a serious 

 drain on the subterranean reservoirs ; but, although Mr. Green's theory 

 does not admit the possibility of any water getting back into these 

 reservoirs, rivers and wells still flow. 



After giving Professor Buckland's illustration of the theory of ar- 

 tesian wells, in which he likens the case in nature to a layer of sand 

 and water between two saucers, Mr. Green says, " Should these excep- 

 tional and assumed conditions occur in nature, the result Avould be 

 substantially as indicated." But we know that similar conditions do 

 occur, and not very rarely either. He continues, "But, as will be 

 seen at a glance, the flow from a well sunk under such circumstances 

 would be limited to the amount of water between the two saucers, and 

 this will be limited to the quantity of rainfall." This is veiy true. He 

 adds, " Since flowing wells and springs are seldom if ever thus limited, 

 we infer that the case supposed does not occur." On the contrary, we 

 have every reason to believe that flowing wells and springs are almost 

 always thus limited. Mr. Dickenson's observations, already quoted 

 by Mr. Green, proved that the quantity of summer water in the river 

 Colne varied with the rain in the preceding winter. In every particular- 

 ly dry summer springs by the thousand are entirely dried up, and the 

 flow from the majority of others is greatly diminished. On the other 

 hand, in wet seasons all but the most extraordinary springs have their 

 flow increased. In some geological formations increase of flow occurs 

 very soon after the beginning of rains. Arago states as the uniform 

 observation of miners, especially those of Cornwall, that in mines sit- 

 uated in the midst of certain limestones water increases in the deepest 

 drifts a very few hours after it has begun to rain on the surface of the 



