AND HOW TO USE IT. 38 



ning under the cover from each side, will imprison the object. If 

 the Dammar wave does not appear to travel freely, a little move- 

 ment with a needle at the edge not touched by the medium will 

 accomplish the purpose, and the slide may then be put away to 

 dry ; but in the case of starches it is not well to put them into a 

 very warm place. The same plan may be adopted with pollens, 

 fern-spores, &c., and the two waves of Dammar will do what is 

 otherwise very difficult, namely, keep such delicate objects in the 

 centre of the slide, where we wish them to be. 



Farrant's medium is used in a similar manner to the above, 

 the chief difficulty being to ring the cover, as the medium does 

 not dry like balsam. The best way to accomplish this is to wash 

 carefully with a soft brush all the medium from around the 

 cover, put the slide aside to dry ; when dry, ring it with white 

 Zinc Cement. When that is dry, thoroughly wash the slide, and 

 give it a second coat. Yet one other process, viz., Carbolised 

 Water, which is useful in cases where the object would be spoiled 

 by the heat necessary to melt glycerine jelly. 



Carbolised Water, about one or two drops of Carbolic Acid 

 to ten ozs. of water. Having an object suitable for this mode of 

 mounting, it may be kept in the preservative fluid till ready, and 

 one of the slides, already prepared with Brown Cement, may be 

 again centered upon the turn-table, and a further coat of the same 

 cement, or some other sticky varnish or gold size, or mastic applied. 

 The cell must then be filled with Carbolised Water, and the object, 

 fresh water algae, diatoms in their natural state, starches, etc., at 

 once put into it ; a cover-glass of the right size having been pre- 

 viously cleaned, it may be taken up in the forceps, and one side 

 being moistened with water, it must be gently lowered upon the 

 convex surface of the fluid, and by its weight it will force out the 

 surplus fluid, which must be absorbed by blotting-paper. As the 

 cover touches the cement, it sticks, and may now be pressed closely 

 to the cell ; but in this little matter care must be exercised, as, if 

 the pressure is applied at one side only, the opposite side rises, 

 and the air enters ; but if the points of the forceps be opened to 

 rather less than the diameter of the cover-glass, pressure may be 

 applied at both edges at the same moment, and repeated applica- 



VOL. IV. D 



