61 



When the microscope reveals that no compound granules remain, 

 the samples are ready for separation into the different grades. Re- 

 move stoppers from the shaker bottles and wash them off carefully 

 with distilled water so as to save all of the adhering particles. Make 

 an apparatus similar to figure using an inverted 2-hole rubber stop- 

 per so large that it will close the mouth of the bottle without going 

 in. Place in one hole a short bent tube and in 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 H 

 inches from the bottom of the bottle. Make a mark on the bottle 3 

 inches from the bottom. Fill the bottles to this mark by means of a 

 small stream of water of sufficient force to thoroughly stir up the con- 

 tents. 



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

 below the end of the tube as shown by a microscopic examination of 

 a sample compared with the sizes of the grades in the preceding exer- 

 cise, the liquid is blown off into a beaker provided for the purpose. 

 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 

 to stand long enough for the sand (.1-1 mm.) to settle below the tube 

 as shown by the microscope and then blow off the fine sand. Repeat 

 until all the fine sand is blown off. The sand and gravel may be sep- 

 arated by the use of the millimeter sieve. 



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

 wrong grade is 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 500 cc. is taken and evap- 

 orated to dryness, placed in a crucible, ignited, weighed and the total 

 amount of clay and silt determined and the percent found. 



The water containing the fine sand, sand and gravel is decanted, 

 each grade is put in a weighed crucible, dried, ignited and the percent 

 of each grade is determined. 



