176 THE AMERICAN MONTHLY [Jimo 



make llie cleaning and preparation of tlie diatoms for 

 study somewliat difficult, or at least a lengthy jirocess. 

 The diatoms are associated with a tenaceous clay matrix 

 very difficult to eliminate by boiling or acid treatment. 

 It may be easily removed by trituration on a soft rubber 

 surface freeing the silicious organisms in abundance; and 

 when they are so freed, it is noted that the surface and 

 interior of the diatoms, especially the Biddulphia, and 

 Actinocyclii, are densely packed with crystalline bundles. 

 These crystals may be removed by digesting in a mix- 

 ture of equal parts of sulphuric and hydrochloric acids. 

 It will also be noted that the larger Coscinodiscii are 

 encrusted with blackish spherules of ironpyrite. This 

 can be removed by digesting in nitric acid. When the 

 acid treatment is properly carried out, fair slides may be 

 prepared ; but while the requirements noted here may 

 seem formidable or tedious, there is a very simple and 

 direct process that any one can use for all essential pur- 

 poses of study. For this purpose it is merely necessary 

 to take a piece of the crude diatomaceous clay as large 

 as a lima-bean, wet it with water, place it in tke palm 

 of the left hand, and crush it down by the pressure of 

 the fingers of the right hand. Then with the tip of the 

 index finger of the right hand the clay is continuously 

 triturated until no visible small particles or lumps are 

 evident. In the trituration, utilize as much surface of 

 the palm as the hand will [)ermit. The triturated layer 

 is tlien removed clean from the hand by a pocket knife 

 blade and transferred to a small shallow saucer-like ves- 

 sel. Water is added, and the paste is dabbled, which 

 will free the diatoms. Allow them to settle to the bot- 

 tom. The clay water is then poured ofl' carefully, and 

 additional water added a few times to remove the remain- 

 ing flocculent matter. Then the diatoms may be readily 

 concenti"ated by a gentle twirling on an incline and tilt- 

 ing to one side. Then a pi})pette Avill remove the dia- 



