232 THE AMERICAN MONTHLY [July 



Assuming that a concentration of a recent marine diatom- 

 bearing material had been made: say, of a gulf or marsh 

 deposit, by the process cited above. In this case, 

 nearly all of the vegetable debris, including carbonized 

 lignitic matter, would come over or out, along with the 

 diatoms. There would occur a difficulty in reducing all 

 of the carbonized material in the boiling acids, and the 

 effort should be made in advance to eliminate this form 

 of debris. 



The following method will obviate this source of 

 trouble: For the purpose it is necessary to have avail- 

 able for use, one or more of the small thin, well known, 

 wooden butter-holders or a hemispherical rubber cup. 

 These vessels have round bottoms and usually when 

 partially filled with a liquid, sit level. The diatomaceous 

 material as roughly concentrated or freed from most of 

 the sand is transferred to the wooden bowl. The bowl 

 is supported on a small plate of window glass to enable 

 it to turn readily and the bowl is then given a smart flip 

 with the tip of the index finger, when it will spin 

 rapidly around a few times. The contained liquid will 

 rise or flare up centrifugally, and spread around the 

 sides, and the heavier sand and vegetable debris will 

 settle back at once, leaving a cloud of diatoms floating, 

 or in suspension. The bowl is then quickly tilted so as 

 to throw the cloud of diatoms towards the edge of the 

 bowl, when several pippetes full of liquid may be quickly 

 removed; this spinning around of the bowl is repeated 

 until it is judged that the diatoms have been separated 

 by gravity gradations from the heavier sediments. 



If the desirable material thus separated is allowed to 

 settle in a suitable holder, and the excess of water then 

 removed, and the diatoms deposited as a drop on a piece 

 of good blotting paper, a ball of diatom material will be 

 thus at once secured; and may be dried immediately 

 over an argand lamp, and when the ball is dried and 



