129 



tauk of 120,000 gallons capacity, and 100 feet above the University cam- 

 ]H]s. Ttie main pipe lines are of S-inch asplialted cast iron witli leaded 

 joints, and for the heavy pressure near the pnnip-house are of double 

 strength. For the present consumption of SO.OfK) gallons per day, a few 

 hours' service every three or four days is all that is required of this 

 l^ump. 



The pond formed by this dam has a water surface of four acres, and 

 is deep and narrow. Its estimated capacity is 20,000,000 gallons. The 

 area of the catchment is approximately 200 acres, most of which is 

 characterized by steep, sparsely wooded slopes. 



The dam was completed in July, 1911, and the pond began to fill in 

 September. There was very little run-off, however, till the loth of Septem- 

 ber, when a three-inch rain raised the pond from a nearly empty condition 

 to within eight feet of the top of the dam. During the remainder of 

 September the pond completely filled, and by the first of October was 

 spilling over the crest. The total rainfall of this period was ten inches, 

 from the first five inches of which there was no immediate run-off of any 

 consequence. In other words, five inches went to replenish the ground- 

 water, after the severe drouth of the summer. No leakage has developed 

 in any part of the structure of the dam, nor in any part of the contact 

 between the dam and the lx)ttora and sides of the valley. 



III. 



The geological conditions of water supply in the limestone region are 

 radically different from those ju.st described for the Knobstone area. 



First of all the slopes are much less steep, and the soil is less per- 

 meable than in the Knobstone region. The soil is also of greater thick- 

 ness and more fertfle. Originally the region was heavily forested, and a 

 few examples may still be seen of virgin forest, as for example, on the 

 University farm at Mitchell. 



The central portion of the region, away from the deep valleys to 

 the east and west, is nearly level, and is the area of the Mitchell limestone, 

 preeminent as a cave-bearing formaticm. In this central portion of the 

 limestone i-egion, nearly all of the drainage is underground, and springs 

 and sinkholes abound'. In many instances the entire headwater portions 



' It is the sinkhole region of Newsom. the IMitchell plane of Beede. See Ncw- 

 som, J. P., A Geological Section Across Southern Indiana from Hanover to Vin- 

 cennes, Proc. Ind. Acad. Sci. for 1897, pp. 250-2.5.3 ; Bccde, J. W., The Cycle of 

 Subterranean Drainage as illustrated in the Bloomington, Indiana, Quadrangle, 

 Proc. Ind. Acad. Sci. for 1910, pp. 81-111. 



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