ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 725 



The advantages claimed for this suhstance, over all others used 

 for a similar purpose, are that it is secure. Such thick objects as the 

 female organs of Vermicularis aud Tricocephalus dispar in glycerine, 

 are now as tight and firm as when first mounted in 1878. It hardens 

 immediately. The moment the heated wire is removed, the specimen 

 may be cleaned and handled without fear, a great advantage over 

 such slow-drying fluids as dammar and balsam. It never runs in, as 

 white zinc and other cements are apt to do. 



Metal Caps for Glycerine Mounts.* — Mr. F. Enock protects 

 objects mounted in fluid from damage by external pressure by a small 

 metallic ring of angular section fitting closely round the outside of 

 the cell and at the same time slightly overlapping the cover-glass, 

 entirely closing in the rim. He writes : — "I have had much 

 bitter experience with preparations mounted in glycerine, which 

 suffer injury from clumsiness in handling, more than the fault 

 of expansion ; for after a preparation has been mounted two or 

 three years, the cement becomes very hard, and if injured by a 

 fall, or knock against the Microscope, starts a leak. The number 

 of preparations ruined by my customers in this and other ways, 

 prompted me to find a remedy, or to lessen the chance of injury. 

 I have now devised the metal caps, which so far have stood 

 the heavy thumps of the Post-office men, and all the clumsy treat- 

 ment which many give them. The caps are made to fit Pumphrey's 

 vulcanite cells, as they are the only cell to be depended upon for size 

 and shape. I never use any other. My plan of using these caps is 

 as follows : — After having fixed the cover properly and without 

 leakage, I wash the preparation under the tap until all traces of 

 glycerine are removed, then run a good thick ring of any kind of 

 cement round the edge of the cover and cell, finally dropping on the 

 cap, when the mount should be placed aside for a week, so that the 

 cement or varnish may properly set. I use these caps 

 for all deep cells, as they prevent the cover from Fig. 141. 

 being pushed off, and am having some made half the 

 depth of those sent, for shallow cells." 



Nassau Adjustable Spiral Spring Clip. — This clip, 

 the construction of which is sufficiently explained by 

 Fig. 141, can be instantly adjusted by a screw move- 

 ment to any degree of pressure required upon the 

 cover-glass in mounting. 



Green Light for Microscopical Observations. — We 

 briefly alluded to this subject in the previous vol- 

 ume,! but it may be well to record somewhat more 

 specifically that Professor T. W. Engelmann strongly recommends 

 the use oi green light for delicate observations; it not only spares 

 the eyes, but also gives images which are markedly sharper than 



* North. Microscopist, i. (1881) pp. 297-8. Journ. Quek. Micr. Club, i. 

 (1882) p. 40. 



f This Journal, i. (1881) p. 224. 



