The Microscope. Xlo 



ing substance. The boiling process above described dispenses with 

 the addition, dnring the cleaning, of any powdered crystalline salts, 

 and is also operated with a minimum of acid Huids. And to purify 

 the diatoms from acids, it is merely necessary to allow the prepara- 

 tion to settle a few minutes, and carefully draw off the bulk of the 

 acid and allow the diatoms to settle in shallow china saucers, half an 

 inch deep preferably; draw off and change the water after one 

 minute intrrvals, and repeat for four or five changes. A trial test 

 made on a slide dried over a flame will show that all acid has been 

 removed from the diatoms. At this stage, we have a rich concentra- 

 tion of the diatoms, but included therein some sand grains and floc- 

 culent soil ; the flocculent matter is removed hj repeated shakings 

 and settlings through a few inches in depth of clean water at three 

 minute intervals, until, when tested under the microscope, a satisfac- 

 tory appearance is reached. 



The acid-cleaned diatoms are again transferred to the crystal 

 . gigging glass, and water added, and then very gently gigged for a 

 final concentration of the diatomaceous forms, and a further portion 

 of fine sand removed. The finishing touch to the cleaning for con- 

 centration of the forms is done by placing a small quantity of the 

 acid-cleaned and concentrated diatoms into a concave black or dark 

 glass, such as is used in tourists' eye-glasses, and the contents gently 

 oscillated from side to side and to and fro, when the diatoms will be 

 found very richly aggregated on the centre of the containing glass; 

 the glass is then tilted and the diatoms removed by the gentle suc- 

 tion of a pipette, the dark glass enabling the mass of diatoms to be 

 distincjuished from the fine grains of sand adherent to the bottom of 

 the glass. In lieu of the dark concave eye-glass, a deep bull's-eye 

 watch crystal makes a good substitute for the final act of concen- 

 tration. 



Diatoms are also richly concentrated from sand by simply 

 spreading the containing fluid over either a six inch square of smooth 

 or ground glass, and gently gigging it while tilting it in the direc- 

 tion of one of the corners, and allowing the fluid to run off into a 

 proper receptacle. A large percentage of the, sand grains remain in 

 situ, or adherent to the glass surface. I have made no allusion to 

 boiling in alkaline solittions to neutralize traces of acids or for any 

 other beneficial purposes, as I have not found it at all desirable or 

 necessary to do so. There are a variety of further useful sugges- 

 gestions that I might enlarge upon, especially as to the uses of 



