316 



cox. 



No apparatus seems to offer advantages over Selione's elutriation apparatus 

 with the modification that it should be supplemented by a second elutriating 

 tube as described by Osborne ^* in which all of the soil except a portion of the 



clay and fine silt is at first placed. The ap- 

 paratus used by me was obtained from Germany 

 and is similar to that described by Schone ex- 

 cept that each unit has the second elutriating 

 tube of narrow bore and with straight sides to 

 precede the Schone's tube proper. A complete 

 apparatus in use by me is shown in figure 8 and 

 figure 9 is a detail picture of the outflow tube. 



The diameters of the two tubes were ac- 

 curately measured and that of their straight- 

 sided parts was found by careful calibration 

 to be comparable, as they should be, in all parts. 

 The diameters of the small tube A and the 

 large tube B calculated aecordiiia: to the formula 



Fig. 8. — ^Modified Schone appa- 

 ratus for the mechan- 

 ical analysis of soils. 



D 



,'4z 



centimeters Avere found to be 2.4.5G 



A Trh 



and 4.990 centimeters respectively. In the for- 

 mula D is the diameter, z the cubic centimetei's 

 of water to a given, exactly measured height 

 (h) of tube. 



By means of the stopcock x controlling the 

 pressure, the feed water can be regulated and 

 the outflow at )/ measured under given heights 

 in the piezometer. The law of hydraulic out- 

 flow enables one to compute the outflow for 

 any given height from a known value according 



to the equation Q := -f!: cubic centimeters where 



Q is the outflow per unit of time and fa) the 

 number of cubic centimeters flowing in (t) units 

 of time. A correction, which for the purpose of 

 this apparatus may be taken as constant, must be 

 subtracted for the retardation due to capillary 

 attraction. This factor (C) may be calculated 

 by measuring the quantity which flows out at 

 two different heights of the colunm of the piezo- 

 meter according to tlie equation 



or C= 



Vh,-C : \'h, 



-C=Qi : Q, 

 cubic centimeters, 



where (h) is the observed height of the water in 

 tlie piezometer. For the most exact determina- 

 tion one chooses the lowest and highest from 

 which an exact reading can be made. I obtained 

 the following results. 



Conn. Agri. Exp. Sta., Ann. Rep. (1887), 144 et seq. 



