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equal ignorance of the effects of the artificial conditions 

 that exist over the whole of the inhabited parts of the town. 

 I mean the dry wells, cess-pools, and middens that are dug 

 in the rock, and which yield a large supply of their watery 

 contents hy percolation through the strata. The percolation 

 of foul matter from some of these receptacles I have in 

 some instances traced to the depth of several feet, and over 

 a considerable area surrounding them. The effects of this 

 contaminating process of filtration through the fractures 

 and strata to the wells I need not attempt to describe. 



In a former part of my paper I stated that several beds 

 or seams of clay, of varying thickness, occasionally inter- 

 vene between the strata. These beds contain large quanti- 

 ties of magnesia, and in the passage of the water over them 

 impart to it considerable quantities of magnesia held in a 

 state of solution. Dr. Brett states that the magnesia gives 

 to the water the quality of hardness much more than lime 

 does, which is also taken up by the water, probably in its 

 passage through diluvial clay containing a large quantity 

 of lime in the form of marl. 



The deeper the sinkings are made in the rock the greater 

 number of beds of clay must be passed through, and further, 

 I am inclined to believe that in the descending series of 

 strata of the lower red, the beds multiply in number. 

 Hence the deeper the sinkings, the harder the water will be, 

 or, in other words, the greater quantity of solid matter will 

 it hold in solution. 



This fact is proved by the water in Messrs. Holme's 

 well, near Benson- street, which, I understand, is very deep, 

 and is situated in the lower red subdivision of the sandstone. 

 By Dr. Brett's analysis of the qualities of this water, it 

 contains double the quantity of solid matter that exists in 

 the wells belonging to the public companies. I have 

 also before stated that the lower beds of the series of the 

 sandstone, which exist between the upper beds and the coal 



