22 



SOME HINTS ON THE PREPARATION AND 



hard surface of iron or steel; after which one end may be inserted 

 into a match by way of handle. The needle should always be 

 warmed over the lamp before thrusting it beneath the covering glass, 

 to avoid the formation of air bubbles. If the balsam first applied 

 be insufficient to fill out perfectly to the edges of the cover, more 

 may be added by means of the glass rod. It will flow under the 

 cover by capillary attraction and fill up evenly all around, if the 

 operation be carefully performed. Then come the final operations 

 of setting away to harden (always in a flat position), and the ring- 

 ing with cement, or not, as the worker's fancy dictates. A mount 

 made in this manner is very simple and easy, requires no outlay for 

 even the materials for the cell, and can be made quite neat and 

 handsome in appearance, as this faithful reproduction of one will 

 testify to the reader's eye. 



The mounting of diatoms in balsam is probably familiar to all 

 of my readers, and yet, I feel impelled to give a few hints on this 

 branch, albeit at the risk of telling what every one already knows 

 full well. I do not propose to touch upon the cleaning of these 

 at present, but presuming all this preparatory work to have been 

 already well done, I will briefly tell how to mount them in an easy 

 and expeditious way. 



Fig. 14. Specimen. 



For this purpose we shall require, in addition to the tools and 

 materials already mentioned, a glass tube about six inches long with 

 a bore of say -f^ of an inch, a homoeopathic vial, or still better one 

 made from glass tubing, of the form shown in illustration, and a 

 brass table, larger and heavier than that shown in our first paper, 

 with spirit lamp. Having these ready, with the cleaned diatoms in 

 the stock bottle, and our balsam, (pure), slips, circular covers, and 

 mounting plate, let us proceed to work. Shake the stock bottle 

 carefully until its contents are evenly distributed throughout, then 

 with the glass tube take up two or three dips and transfer to the 



