J. M. Blake — Improved Method of Cleaning Diatoms. 21 



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 millimeter, 

 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 com- 

 posed 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 fine sand are to be gradually worked 

 out by the alternate pressure and release of a rubber compres- 

 sion bulb. The size used on camera shutters answers very well. 

 This bulb is placed on the end of a glass tube six or seven 

 inches long. It is desirable, but not essential, to have a bulb 

 blown in the middle of this tube. A short bit of rubber tub- 

 ing of proper diameter is slipped over the free end of the glass 

 tube, and this is to be inserted in the mouth of the vial so as to 

 make a tight joint, but this joint should be easily separable. 

 In operation we take up a small portion of the material in a 

 dropper, and squeezing it into the vial, we insert the rubber tip 

 of the glass tube, and holding the strainer under water, press 

 on the bulb, which will cause the air, acid, and salts to flow out 

 together with a cloud of fine waste material. The pressure is 

 now to be alternately applied and released, and the waste mate- 

 rial is thus gradually removed. The discharge of clay and fine 

 sand at last ceases, and the diatoms are left with the coarse 

 sand and mica, which can be removed by other means. 



By thus eliminating the clay we will have disposed of one of 

 the most serious obstacles to the cleaning of diatoms. One 

 very important advantage of this method of working is the 

 small quantity of material required because there is very little 

 waste. Successive portions as they are cleared can be united to 

 make up the needed amount. 



It is important that the strainer should not be overloaded, 

 for that would cause it to pack and choke. This pack has to 

 be broken up by shaking after each compression, more partic- 

 ularly in cleaning filamentous forms, in order to allow the 

 imprisoned debris to escape at the next compression. As a gen- 

 eral rule, and with the more granular forms, this packing 

 requires only a little attention to avoid trouble. Violent com- 

 pression will fracture many of the larger and more fragile 

 forms of diatoms. The strainer vial should be kept in water 



