ZOOLOGY AND BOTANY, MICKOSGOPY, ETC. 123 



a spirit lamp. A groove is then turned round the corner of the lens, 

 as shown, by means of a keen splinter of diamond, and the supporting 

 plate turned to fit the groove, which plate is afterwards cemented or 

 burnished in the front of the setting. To avoid risk of pushing the 

 lens in by pressure, the face should not be quite flush with the front 

 of the plate. 



Fig. 13. Fig. 14. 



" To cement the lens into the plate, lay this on a piece of tissue 

 paper set on the hot plate, put a fragment of sulphur into the ring, 

 and the lens on the top of this. When the sulphur has melted, press 

 the lens well down into the ring. After the whole has cooled, the 

 surplus sulphur comes off by a pull with the paper. In turning out 

 the groove at the corner of the balloon lens, there is but little risk of 

 splintering the glass, if a suitable diamond point is used. The small 

 fracture in the lens shown, was occasioned by the use of a ring emery 

 grinder, rather too small, intended to take off the rough cut of the 

 diamond ; but I consider this after smoothing operation unneces- 

 sary, as it is more hazardous to use than the diamond itself. 



" I have found the best way of mounting these diamond splinters 

 to be thus : Take a short piece of copper wire, and split the end down 

 about one-eighth of an inch with a watch-spring saw ; open out the 

 split and anneal the end by heating it red hot. Lay the splinter 

 of diamond on one of the open sides, sticking it on with a touch of 

 Canada balsam. When the point appears fairly projecting in the 

 direction required, close the split together with pliers, well pinching 

 it on to the diamond ; this becomes imbedded in the soft copper. 

 Finally, by means of the blow-pipe and borax, run silver solder into 

 the slit, and thus the diamond will be very securely fixed." 



New Homogeneous-immersion Fluid of 1*5 Refractive Index. — 

 Mr. Charles H. Bassett, of Boston, U.S.A., has recently communicated 

 through Mr. Tolles a formula for a new immersion-fluid, which has 

 proved successful with Mr. Tolles's high-angled homogeneous- 

 immersion objectives. We quote from Mr. Bassett's instructions : — 



" The formula for the new ' homogeneous-immersion fluid ' of re- 

 fractive index 1 • 5 is : — 



Schering's chloral hydrate, in crusts . . . . grs. 485 

 Bower's pure glycerine grs. 70 



Mix, and dissolve in an open-mouthed bottle by means of a water 

 bath. 



" No special manipulative skill is required in the preparation of 



