1882.] 



MICEOSCOPICAL JOURNAL. 



115 



adhered to it from the cloth. Care 

 is taken that none adhere. In this 

 way the material is all worked over 

 and this treatment has to be repeated 

 perhaps many times before the ma- 

 terial is sufficiently rid of the sand. 

 It may be that before this is accom- 

 plished, the sand and diatoms will 

 cling together on the slide, causing 

 considerable loss of the latter. This 

 is owing to little particles of matter 

 getting into the material from the 

 cloths, or from the air, and cannot be 

 prevented. As soon as this clinging 

 is detected, which is easily done by 

 occasionally examining the slide un- 

 der the microscope, first drying it 

 after pouring off the material, the 

 latter should be boiled for a minute 

 in sulphuric acid, to which is added 

 a little chlorate of potash while boil- 

 ing. Of course the diffused material 

 is poured into a beaker, allowed to 

 settle, and the water drained off. It 

 is then washed and the treatment 

 continued. When the material is at 

 last freed of sand, it is boiled a last 

 time in sulphuric acid, chlorate of 

 potash being used as before. It is 

 then thoroughly washed and properly 

 diffused in dilute alcohol for mount- 

 ing. The alcohol should be filtered 

 as well as the water. 



In this last process some of the di- 

 atoms will adhere to the slide, but 

 this is of little consequence if there be 

 plenty of material. As the cloths get 

 pretty wet, as they will, they should 

 be exchanged for dry ones. 



Such is the treatment of fresh-mud 

 material. Lacustrine (sub-peat), sedi- 

 mentary deposits and guano, are 

 treated in the same way. 



The treatment of hard, sub-plutonic 

 and fossil material is somewhat dif- 

 ferent. This material is often very 

 hard and has to be reduced to pow- 

 der. This is accomplished by boil- 

 ing it in a solution of caustic potash 

 — liquor potassa. This should be 

 cautiously used, as too much boiling 

 in it will injure the diatoms. Boiling 

 in a strong solution of carbonate 

 of soda will often accomplish the 



same end, though not so easily, but 

 its use is safe. As soon as a portion 

 of the material has fallen in powder, 

 it should be poured into a large 

 quantity of water, and the remaining 

 lumps boiled in the solution of potash 

 or of carbonate of soda ; this is to be 

 repeated till the whole has been re- 

 duced to powder. The treatment is 

 then by acids, etc., as with fresh-mud 

 material. Fresh-mud material should 

 not be allowed to dry, as it is then 

 very difficult to reduce it to powder. 

 When dried hard, perhaps the best 

 way is to first burn it in a crucible, or 

 in an iron pan over a hot fire ; the 

 organic matter will be pretty well 

 burned out of it, and it is reduced to 

 powder. 



There are generally, I may say al- 

 always, many broken diatoms in sub- 

 plutonic and fossil material. It is 

 very desirable to get rid of these. It 

 may be accomplished in a great 

 measure by using the slide as for get- 

 ting rid of sand. The broken di- 

 atoms adhere by their rough edges to 

 the surface of the glass, whilst the 

 whole diatoms float off ; but more 

 will be lost, perhaps, than when get- 

 ting rid of sand in this way. 



When the material is pure, as in fila- 

 ments, or when attached to algae, it is 

 boiled in the acids, very gently if the 

 forms are delicate. The action of the 

 acids, chlorate and bichromate of 

 potash, and the washings remove all 

 organic matter and leave the diatoms 

 pure. 



Colorado Springs, Col. 



EDITORIAL. 



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— The sixth and last part of Saville 

 Kent's " Manual of the Infusoria " 

 will doubtless be issued in London 

 by the time this Journal reaches its 

 readers, and will soon be in the hands 



