498 SUMMARY OF CURRENT RESEARCHES RELATING TO 



has been noticed in any published directions for treating diatoms. 

 Therefore, the way seems open for a revival of interest in the subject, 

 and this method by which, for instance, a small test sample of diatoms 

 can be cleaned in five minutes' time from the acid-prepared material, 

 should appeal to novices as well as experts, by reason of its saving of 

 both time and effort. 



The first attempt to supplant the ordinary method of separation and 

 cleaning was made by using a cloth sieve made of partly worn cotton 

 •cloth stretched on a frame. The diatom material was treated in the 

 usual way, in a separate vessel with acid. Then, when it had been 

 largely diluted with water, the mass was placed in this cloth-bottomed 

 tray, and agitated and jarred to carry off the clay through the cloth. 

 More water was then added, and the process repeated until only sand 

 and diatoms remained. This plan was not wholly satisfactory, since a 

 large proportion of the diatoms passed through the cloth ; yet a con- 

 siderable bulk of partly cleaned diatoms was obtained, and by careful 

 straining through a sieve the largest diatoms were separated from the 

 smaller and the broken forms, and in this way were secured entirely 

 free from debris. There was an abundance of this material for dis- 

 tribution. 



Very soon after this first experiment, the writer originated an im- 

 proved and more practical method which depended for its success upon 

 the use of cross-sections of wood. Coniferous wood is the most suitable, 

 since it has pores of nearly uniform size, whereas other kinds of wood . 

 nearly always have large and small pores commingled, which make them 

 entirely unsuited for the purpose. These wood cross-sections bear dilute 

 acid without injury, which would not be the case with a metal strainer 

 of equally fine mesh, even supposing such a strainer could be made. 

 Furthermore, such a strainer would be too frail to stand the required 

 pressure. 



A. sharp, thin- edged chisel is used for making the sections, and the 

 wood is kept in boiling water, and removed instantly before each cutting. 

 It requires some care to secure an even thickness, which should be from 

 one-quarter to one millimetre, as needed. The cut section is now to be 

 wetted and surface-dried, and then cemented to a vial, the bottom of 

 which has been cut off for the purpose. A very convenient size can be 

 made from a two-dram vial, making the working aperture of the strainer 

 about one-half inch The cement may be composed of rosin toughened 

 ' by wax. Larger strainers may be made, but this size will answer for 

 the first trials. 



The digested diatom material, moderately diluted, is to be worked 

 through the wood, a small portion at a time. The acid and the salts 

 will pass with some freedom through this wooden grating, and the clay 

 and line sand are to be gradually worked out by the alternate pressure 

 and release of a rubber compression bulb. The size used on camera 

 shutters answers very well. This bulb is placed on the end of a glass 

 tube (! or 7 in. long. It is desirable, but not essential, to have a 

 bulb blown in the middle of this tube. A short bit of rubber tubing of 

 proper diameter is slipped over the free end of the glass tube, and this 

 is to be inserted in the niouth'of the vial so as to make a tight joint,. 



