PRACTICE XXXIII (Continued) 



Place in one hole a short bent tube and m the other a long tube 

 that reaches near the bottom of the bottle. The lower end of 

 this tube should bend suddenly upon itself so that the opening 

 shall be upward and not downward. Adjust this tube when the 

 apparatus is in place on the bottle so that the opening in the 

 long tube will be 1^ inches from the bottom of the bottle. Make 

 a mark on the bottle 3 inches from the bottom, and fill to this 

 mark by means of a small stream of water of sufficient force to 

 thoroughly stir up the contents. 



After the liquid has stood long enough for the fine sand to 

 settle below the end of the tube, as shown by a microscopic ex- 

 amination of a sample compared with the sizes of the grades as 

 determined in the preceding exercise, the liquid is blown off into 

 a beaker provided for the purpose. Pour this into a large glass- 

 stoppered bottle. This operation of filling, settling, and blowing 

 off is repeated until the grades that settle are free from silt and 

 clay. The liquid blown off contains silt and clay, and no effort 

 is made to separate them here. 



For separating the fine sand, fill the bottles as before and allow 

 them to stand long enough for the medium and coarse sand to 

 settle below the 1^-inch mark, as shown by the microscope, and 

 then blow off the fine sand. Repeat until all the fine sand is 

 blown off. The medium sand is separated from the coarser 

 grades by washing it through a 0.32-mm. sieve, and the coarse 

 sand from the gravel by washing through a 1-mm. sieve. 



If at any time during the analysis it is found that some of the 

 larger grades are blown over, it will be necessary to recover this. 



The water containing the silt and clay is poured into a large 

 bottle and thoroughly shaken, when an aliquot part or one tenth 

 is taken and evaporated to dryness, placed in a weighed crucible, 

 ignited, weighed, and the total amount of clay and silt deter- 

 mined and the per cent found. 



The water, containing the fine sand, sand and gravel, is de- 

 canted, each grade is put in a weighed crucible, dried, ignited, 

 and the per cent of each grade is determined. 



References. 



" Soils," Lyon and Fippin, pp. 69-79. 



"The Soil," Hall, pp. 32-56. 



*^ Physical Properties of Soil," Warington, pp. 5-23. 



"The Soil," King, p. 70. 



"Soils," Hilgard, pp. 88-106. 



68 



