"90 TRANSACTIONS OF THE [jAN. 31, 



especially is that the flow of water from all directions towards 

 the wells will, under the high pressure created by the pumps, 

 follow only the larger pores and crevices underground, and by 

 continually enlarging these, create in time a system of channels 

 leading directly to sources of pollution. Such action would 

 annul the filtering power of the soil, upon which so much depends 

 where subterranean waters are used. 



The operation of the great system of gang-wells wliich now 

 supplies about one-sixth of all the water used in Brooklyn illus- 

 trates these principles upon a large scale. Seven million gallons 

 of water are daily drawn from a system of 100 wells, varying in 

 depth from 45 to 100 feet and covering a line about 400 feet in 

 length. Such a yield corresponds to a total rainfall of 32 

 inches a year upon 3,000 acres, or roughly represents the same 

 annual rainfall upon all of the land within a radius of IJ miles 

 from the pumping station. Owing to the sudden demand for 

 this water, the soil waters must be continually drawn downward 

 in the vicinity of the pumps, and the nearer regions must be 

 more effectually drained than the more remote. The predicted 

 consequences are abundantly realized. Shallow wells in the 

 neighborhood are wholly or nearly dry since the pumping station 

 has been opened. A swamp formerly existing about the station 

 has been dried up. The subsoil of the Jewish cemetery 370 yards 

 distant, which offers frequent opportunities for observation, is said 

 by the sexton to be much drier than heretofore. The existence 

 of filthy barnyards and open house drains close to the wells, and 

 richly manured fields all around them, are suggestive features of 

 the case. 



Chemical analyses of the water from these wells show an 

 abundance of nitrates, the sure indicators of organic decomposi- 

 tion. 



The gang-well system may be, under proper precautions, of 

 great benefit to communities seeking new supplies of water, but 

 it is open to abuses in its applications which render it hardly less 

 safe in the long run than the ordinary well. From a very large 

 number of analyses of the water of small driven wells made by 

 myself, I am convinced that the causes of deterioration in such 

 wells rest also upon the principles already outlined. 



