COLLECTING AND PREPARING. 8ii 



Washing the Clay for Microscopic Organisms. — The following 

 method is recommended for obtaining microscopic organisms from 

 the clays resulting from the disintegration of the shales : 



'' In preparing most of the samples of clay, we would put about 

 one ounce of the material and the same amount of common wash- 

 ing soda into a druggist's two-quart, clear-glass packing bottle, 

 not over one fourth filled with water, and let it remain twelve to 

 twenty- four hours, frequently shaking the bottle, so as to 

 thoroughly break up the clay. Now fill the bottle with water, and 

 after twenty-five minutes carefully pour off the upper three fourths 

 of it. Again fill with water, and in twenty five minutes decant as 

 before; repeating this at twenty-five minute intervals until the 

 upper three fourths of the water in the bottle, after a twenty-five 

 minute rest, will be nearly clear. A large amount of the fine sand, 

 clay, and soda has by this process been washed, and the action of 

 the soda has broken up the clay and removed most of the adhering 

 material from the fossils. Now mount a few microscopic slides 

 from the residuary sands, etc., at the bottom of the bottle, by tak- 

 ing up with a pipette (a piece of small glass tubing makes the best 

 pipette) a small amount of the material; scatter very thinly over 

 the middle of the slides ; dry them thoroughly over an alcohol 

 lamp, or in some better way, and, while hot, cover the dry material 

 with a few drops of Canada balsam, keeping the slides quite warm 

 until the balsam will be hard when cold. As these '' trial slides " 

 are seldom of any value, it is not necessary to use cover glasses if 

 the balsam is hardened as above directed. A careful examination 

 of these slides under the microscope, with a good quarter- or half- 

 inch objective, will decide as to the value of the material under 

 observation; and if it proves to be only sand, pour it all out, wash 

 the bottle, and again try the same process with another sample of 

 clay. But if the slides show a few good fossils, the next step is to 

 separate them as much as possible from the mass of sand, etc., 

 with which they are associated. In this, as in the first washing, 

 specific gravity will do most of the work. Pour off most of the 

 water and put the shells, sand, etc., into a four-ounce beaker (or 

 glass tumbler), wash out the bottle, fill the beaker about three 

 fourths full of water, and, after it has rested ten minutes, pour 

 three fourths off the top, through a glass funnel into the bottle, 



