114 



THE AMERICAN MONTHLY 



[June, 



How to Imlbed in Paraffiiie. 



While I have often seen paraffine 

 recommended as an imbedding ma- 

 terial, the manner of using it I have 

 never seen published. I therefore 

 offer the following method of my 

 own to the readers of the Journal. 



Make a short paper tube the same 

 size as the well-hole of the section cut- 

 ter, by rolling a strip of paper around a 

 cylinder ; fit a cork to one end of the 

 tube and attach to the upper side of 

 the cork, by cement or otherwise, the 

 specimen you wish to cut (previously 

 hardened in alcohol, if necessary), in 

 such a manner that it will stand up- 

 right in the centre of the tube ; now 

 fill the tube with melted paraffine ; 

 when cold remove the paper, and 

 you have a plug of parafifine enclosing 

 the specimen. I usually make several 

 of these plugs at a time, and keep 

 them in alcohol until wanted. 



I have only used parafifine in this 

 way for cutting vegetable sections, 

 but I see no reason why it is not 

 equally well-adapted for any other 

 soft substance. 



E. L. Cheeseman. 



Knowlesville, N. Y. 



o 



Cleaning Diatoms. 



The following process is the result 

 of a recent fortuitous experiment. 

 Let us suppose that we have suc- 

 ceeded in bringing a quantity of dia- 

 tomaceous material to the state of a 

 beautiful white powder, as previously 

 described, by the use of the bi-sulphate 

 of potassa, or the more easily pro- 

 cured substitute suggested. We then 

 proceed as follows : Procure a piece 

 of silk about four inches square, of 

 good quality and of very close tex- 

 ture ; moisten it thoroughly at first, 

 and, in its depressed centre, place a 

 small portion of the fused material to 

 be cleaned ; then add to it several 

 drops of water to bring it in solution, 

 collect the sides and corners of the 

 silk together, twist them to prevent 

 the escape of material or fluid, com- 

 press immediately above the material. 



and carry the pressure down gradu- 

 ally, without, however, bringing the 

 pressure of the fingers to the bot- 

 tom part of the silk ; this compres- 

 sion forces out the water, and with 

 the water a large percentage of the 

 undesirable impurities contained in 

 the material, while the close texture 

 of the silk holds back the various 

 diatoms and discs, with the larger 

 particles of sand. After the first 

 compression a few more drops of 

 water are added and the pressure re- 

 newed as before. The silk is then 

 turned inside out, and washed by 

 gentle shaking in a deep watch-glass 

 to remove the diatoms, etc. We now 

 note an absence of milkiness in the 

 product, and the cleaned residue re- 

 mains at the bottom of the crystal ; 

 by transferring this to a deeper re- 

 ceptacle, we can then dip up the dia- 

 toms with a pipette to mount direct 

 on slide or cover-glass. This method 

 gives surprisingly fine results. 



A knowledge of the two methods 

 of operating on diatomaceous mate- 

 rial, as communicated by- me, will 

 enable the possessor of a suitable mi- 

 croscope to launch into the prepara- 

 tion of diatoms for study, with suc- 

 cess at the outset. 



K. M. Cunningham. 



EDITORIAL. 



— The first part of the " Catalogue 

 of the Diatomaceae " is partly printed, 

 and will probably be completed this 

 month or in July. The fourth 

 part of Kent's " Manual of the Infus- 

 oria " has been issued. The third 

 fasicle of Van Heurck's " Synopsis of 

 Diatoms," which has been unexpect- 

 edly delayed, is expected this month. 



A Scientific Exhibition. — On the 

 17th of August the American Associ- 

 ation for the Advancement of Science 

 will meet in Cincinnati. On the 8th 

 of September the Annual Cincinnati 

 Exposition will open, to continue a 

 month. At the Association meeting 



