369 



at elevtations of sixty-one, one hundred and twenty-four, or one hun- 

 dred and sixty feet, as the case requires, thus reducing the work and 

 cost of pumping to its minimum. 



The water from the reservoir will he taken into the pipe distribu- 

 tion system, to he used at the hydrants, drinking fountains, &c, at 

 different points on the park. This will constitute hut a small pro- 

 portion of the water required on the park. By far the largest quan- 

 tity will be required to supply the loss from the lake, due to 

 evaporation from the surface and leakage from the bottom. This 

 water may be used to produce pools, cascades, rapids, and running 

 brooks before it empties into the lake. 



SOURCE OF WATER SUPPLY FOR THE WELL. 



The ground on that portion of the park lying south of the hills, 

 and in fact all of the south side of Long Island, is one vast bed of 

 sand, which is generally covered by but a few feet of soil and loam. 

 On account of this peculiar formation, a large proportion, probably 

 sixty per cent., of the rain fall is absorbed, and passes down to what 

 is popularly known as " the main spring." This is a body of water 

 filling the sand, and extending under this whole district. The dis- 

 tance from the surface of the ground to the surface of this body 

 of water depends upon the modulation of the ground ; but the 

 elevation of this water surface above tide level is quite uniform 

 for equal distances from tide water, and depends upon that dis- 

 tance ; it rises about seven feet per mile — so that, for instance, at 

 any point two miles from tide water, the surface of this subter- 

 raneous reservoir will be about fourteen feet above tide level. 

 The slope being known, it becomes an easy matter to calculate 

 with great certainty the quantity of water which can be obtained 

 from the well. 



The rain fall averages something over forty inches per annum, 

 but assuming it to be forty inches, then sixty per cent, of this, or 

 twenty-four inches in depth of water, will reach the main spring. 

 This quantity over a circle, with a radius of one-half a mile will 

 give a daily supply of about nine hundred thousand gallons. To 

 draw this supply of water to the well from a distance of one-half 

 a mile, it will be necessary to pump the water down to a depth of 

 about three and a half feet, and this will allow the water to take 

 the regular slope of about seven feet per mile. The water in 

 the well is twelve feet deep, and can readily be pumped down 

 seven feet, and this will draw water from nearly a mile in every 

 direction. There is, therefore, an abundant supply of water 

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