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lOiirth (lams will imt onliiiiiril.v hu feasible in tiie Kiinlistonc region, 

 (twinjj to the iieiieral laclv of clay of good imddliiig (niallties for the 

 core or the (lain. In the edge of the limestone region sudi day may he 

 avaihdile, hnt wonld in most cases have to he moved ddwn very steep 

 i-lopes at considerable expense. Exce]it on large contracts, where the 

 construction of a cable-way wouhl be worth wliile, the use of clay for 

 short dams would i>r()b;d)ly be more expensive than concrete'. In some 

 instances it might he advisable to use earth eml)an!<ments with a rein- 

 fcreed concrete core, mortised well into the rock, and extending to the 

 top of the structure. With this type of construction any sort of material, 

 having the requisite stal)ility, could lie used for the embankments, shice 

 the waterproof (lualities of the dam would de]H'nd entirely on the core. 

 (Jreat care is necessary in this typo of dam to prevent settling of the 

 embankments in such a \Aay as to warp or crack the core. It is best that 

 no water should l)e allowed to come against the dam until thorough 

 settling has taken place. For long dams in the Kuobstone region some 

 such construction as that just described is almost a necessity.- It may hi 

 said finally that timber dams are ')nly makeshifts, and should not be 

 tolerated by any community. 



As an example of a successful concrete arch d.-ini in the Kuobstone 

 region, a brief descrijition may be given at this point of the dam re(_t'ntly 

 built by Indiana University. The cross-section of this dam is shown in 

 the accomi)anying figure (Fig. 1), and photograi>hs of the dam and 

 l)ond in Figs. 2, ."> and 4. The length of the dam on the rock substratum 

 is llGl feet, and on the crest litXt feet. 'I'lie thickness at the base is 

 2SA feet, and the tot.al height subject to watci' iiressure is .".4 feet. Tlie 

 niiiximum height above the valley alluvium is I'S feet. The dam is 

 stepped up in ledges on iioth the uii-stre.im and down-slre:im faces, and 

 the cross-section is such (bat ample stability is imivided. even without any 

 arching. Tiu' .•u-ching (to a radius of ."'.Ki feet) gives very greatly in- 

 creased stability under water pressure, and vastly decreases the liability 



' -Vs a mattci- (ir r:i,.| ii,.:uly all dl' llu' liids on cartli .lams i",ir the Hidvorsit.v 

 were hii,'licr lliaii on (hr lyp,. of ,oii,it|,. daiii ronsi ni.i.il, and lo be dosi'riliod 

 later. 



= -V type of dam, <-(insistin'; <<( a lliin plali' of rrinloiciMl concrctf. snpportcd 

 liy bnttrcsscs of con.rrlc is disciilMii in i!u<l and Hill's ii-callsi- on roinforced con- 

 crete, and has aclnally lni'ii consl ni.lrd. in ;\ lew cas.'s. This type of dam uses a 

 minimimi of .sUmk Imal maliiial, l>ul d.niamls a coiisiderahle outlay for forms. 

 It would prohahly idsi ahoui I he sam.> as a L^ood lulilile oni-rete dam. 



I 



