Van Nostrand's eclectic engineering magazine . place under-neath the points of greatest elevation. Sub-sequent to the upheaval and consequentdisplacement of the strata, the process ofdenudation has taken place, cutting the up-per beds, and leaving the outcrop exposed,not only inside the basin, but in the adjoin-ing valleys at 0 and 0. Now, it is evidentthat if the highest ridges bounding the val- ley be taken to mark the line of water-shed, and therefore limiting the area of thecatchment basin, it is possible that the esti-mate of the amount of supply may be foundfar short of what the district
Van Nostrand's eclectic engineering magazine . place under-neath the points of greatest elevation. Sub-sequent to the upheaval and consequentdisplacement of the strata, the process ofdenudation has taken place, cutting the up-per beds, and leaving the outcrop exposed,not only inside the basin, but in the adjoin-ing valleys at 0 and 0. Now, it is evidentthat if the highest ridges bounding the val- ley be taken to mark the line of water-shed, and therefore limiting the area of thecatchment basin, it is possible that the esti-mate of the amount of supply may be foundfar short of what the district will yield. Acertain proportion of the rain failing uponthe outcrop at the points 0 0 will be ab-sorbed by such of the strata as are porous,and the water, percolating through the bed-ding, till an impervious stratum is metwith, will find its way down the course ofthe stratification, till it ultimately reachesthe reservoir in the form of springs, andcontributes more or less to the maintenanceof the supply. The converse of this condi- TiG. SECTION ACKOSS ANTICLINAL AXIS. tion of things will be readily understood byroference to Fig. 2. It also represents asection taken directly across the valley of the proposed reservoir. Here the strata ofthe earths crust incline against each otherconsequent upon some disturbing force DESIGNING AND CONSTRUCTION OF STORAGE RESERVOIRS. having taken place to elevate them, andare said to be anticlinal to the axis of thevalley. In order to account for the forma-tion of a valley on the summit of the ridge,that at first was thrown up, it is to be un-derstood that the upper beds suffered frac-ture in the process of upheaval, and subse-quently were exposed to denudation. Thesevalleys of elevation are evidently not to bedesired as situations for the establishmentof storage reservoirs. The area of thegathering grounds will be much more lim- ited than the extent of the watershed wouldappear to indicate ; and cannot safely berelied upon to give an estima
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Keywords: ., bookcentury1800, bookdecade1860, bookpubl, booksubjectengineering
