856 



SUMMARY OP CURRENT RESEARCHES RELATING TO 



Fig. 233 



Tlie colour is a dark sherry, but the medium is transparent and brilliant, and 

 is excellent for sections of potassium nitrate made parallel to the axis. 



Solution number 1 is suitable to perishable 

 crystals, as plumbic acetate, Eochelle salt. 

 Number 2 is best fitted for attaching crystals 

 or sections of any kind, or for holding sec- 

 tions to be ground very thin. Number 3 is 

 preferable to Canada balsam on account of its 

 white colour. It serves well to mount sepa- 

 rately halves of the same crystal section, and 

 is a capital cement for these two mounts when 

 crossed. Numbers 4 and 5 are preferred by 

 the author as they are perfectly free from 

 humidity, and though darker than fresh 

 Canada balsam, their tint does not deepen 

 by time. A sixth medium, of which Prof. 

 Johnston has had less experience, but of 

 which he speaks favourably, especially for 

 potassium nitrate, is made by boiling the 

 whitest dammar until the scum is nearly 

 dissipated ; the rest of the scum is then 

 spooned off. Rectified spirits of turpentine 

 are then added till the proper tenuity is 

 attained. It is then passed while still warm 

 into a bottle, or the dammar having been 

 boiled may be allowed to cool and then broken 

 up into small pieces ; these pieces are then 

 put into a bottle and covered with rectified 

 spirits of turpentine, the solution being left 

 to time to accomplish. 



Bausch & Lomb Optical Co.'s Spirit- 

 lamp. — The peculiarity of these glass lamps is 

 that they have nine facets, so that they can 

 either be used upright on a mounting stand, 

 as in fig. 233, or inclined as in fig. 284. 



The size of the flame may be regulated by a sliding tube. In use the lamp 



is filled only one-third full. 



Bbiant, T. J.— New Form of Microscopic Cell for mounting objects requiring to be 

 examined on both sides. 



[A piece of cardboard, the size of the usual glass slip, and having a circular aper- 

 ture punched in its centre, is pasted between two similar cards with apertures 

 slightly larger. A ring of Miller's cement is then run round the edge of the 

 inner card,°on one side of which a cover-glass is fastened, thus forming a fluid- 

 tight cell. ' In this the object is placed, and is secured by another cover-glass, 

 also fitting the aperture of the outer card. Objects mounted in this way may 

 readily be examined with high powers, both on their upper and under surfaces.] 

 I6th Ann. Rep. S. Lond. Micr. and Nat. Hist. Club, 1887, p. 12. 

 Neville, J.-New Form of Dry Cell. 



[" Made of vulcanite, which he had named the wmdow-slide. Ihis cell allows the 

 cover-glass to be slipped on and off at pleasure, so that objects may be at once 

 put up for examination, and dust or damp on the glass at any time removed."] 

 \&th Ann. Rep. S. Lond. Micr. and Nat. Hist. Club, 1887, p. 12. 

 PiNCKNET, E.— Slide-Index. . 



[Considers that the catalogues prepared by Ward and others may serve their 

 purpose as a record, but not as an index. Every worker needs a reliable slide- 

 index, to which he may turn for instant reference, and lie therefore suggests the 

 following: — Take a six-quire blank book, commonly known as "record" form, 

 plain blue lines for writing and one vertical red line about one inch from left- 



