256 



HARDWICKE'S SCIENCE-GO SSIT. 



wet camel-hair pencil; then carefully varnish by 

 hand, not on the turntable, for fear of disturbing 

 the cover, running the varnish into the angle formed 

 by the junction of the cover and cell, and including 

 the smallest possible portion of both cover and cell ; 

 next day, when the varnish is dry, place the prepa- 

 ration under a stream of water, either a tap turned 

 gently on, or the wash-bottle, to wash away the 

 whole of the glycerine from the surface of cell and 

 cover, as until this is done effectually the varnish 

 will not adhere and make a good joint, hence the 

 reason of covering the smallest possible space with 

 the first coat of varnish. Dry carefully, and then 

 revarnish. The turntable can now be used : if there 

 is any doubt about the removal of surplus glycerine, 

 wash again. Repeat the varnishing until a good 

 amount is accumulated, not neglecting the junction 

 of the cell and slide. As the shellac varnish be- 

 comes somewhat brittle after a time, give a few 

 coats of gold- size for further security ; gold-size is 

 the most reliable of varnishes, and stands well so 

 long as contact with the almost universal solvent 

 glycerine is prevented. The system of compound 

 varnishing is useful in many other cases where the 

 varnish used in retaining the fluid is not altogether 

 reliable- W. T. S. 



Mounting Mites.— For mites try castor; it 

 succeeds well with some insects. Place the insects 

 in a bottle of the oil, and leave until required for 

 mounting; the longer the better. Liquid glue is 

 the proper cement, followed with gold-size (see 

 reply to " E. E. Fletcher," on " Glycerine Mount- 

 ing"); very great care is required in cleaning off 

 the surplus oil from the cell and cover ; it is best done 

 with a camel-hair pencil moistened with benzole. 

 Unless every trace of grease is removed, do not 

 expect the varnish to hold. Weak alcohol can be 

 kept in with gold-size. For strong alcohol try 

 gelatine, followed by gold-size ; respecting this the 

 writer has no experience. 



Cleaning Diatoms.— The following quotations 

 from " The Microscope and its Revelations " will 

 doubtless supply " St. T. H." with the information 

 he requires. After describing the treatment of the 

 diatomaceous deposit with acids, Dr. Carpenter 

 goes on to say (5th edition, p. 344) : — " The sepa- 

 ration of siliceous sand, and the subdivision of the 

 entire aggi'egate of diatoms into the larger and the 

 finer kinds, may be accomplished by stirring the 

 sediment in a tall jar of water, and then, while it is 

 still in motion, pouring off the supernatant fluid as 

 soon as the coarser particles have subsided ; this 

 fluid should be set aside, and as soon as a finer 

 sediment has subsided it should again be poured 

 off; and this process may be repeated three or four 

 times at increasing intervals, until no further sedi- 

 ment subsides after the lapse of half an hour. The 



first sediment will probably contain all the sandy 

 particles, with, perhaps, some of the largest dia- 

 toms, which may be picked out from among them ; 

 and the subsequent sediments will consist almost 

 exclusively of diatoms, the sizes of which will be 

 so graduated that the earliest sediments may be 

 examined with the lower powers, the next with 

 medium powers, while the latest will require the 

 higher powers." — W. B. H. 



h On Mounting.— Mastic is not soluble in tur- 

 pentine, spirit being the best solvent ; it ia also 

 soluble in chloroform, but, like many other gum 

 resins, it contains several constituents, some of 

 which are insoluble in spirit, some in turpentine, 

 and some in chloroform. The evaporation of any 

 of the solvents would throw down the resin it had 

 held in solution, and a pseudo-crystalline appear- 

 ance would become visible, as seen in all the slides 

 mounted in medium named. Why not use pure 

 Canada balsam ? Twenty-five years' experience in 

 mounting Diatomacere satisfies me that no medium 

 is so suitable, and none easier to use, provided it has 

 not been mixed with benzole, turpentine, or chloro- 

 form, either of which will produce bubbles. When 

 the slide is heated, pure balsam may be hardened 

 without air-bubbles making their appearance. Dilute 

 gum-water is the only medium I know of fixing 

 diatoms, &c.— F. K. 



Interference oe Light. — In using my \ objec- 

 tive (100°) with second eye-piece, I find the centre 

 of the field filled with a peculiar brightness that 

 seriously interferes with my view of the object. 

 Can any one tell me what is the cause, and how to 

 get over it ?—</". G. B. Pmcell. 



ZOOLOGY. 



White Woodcock. — It may interest your 

 readers, who, like myself, are lovers of ornithology, 

 to state that a white woodcock (Scolopax rusticola), a 

 male, was shot on Strensall Common, near York, in 

 October last, and is now in my possession. I think 

 it is unusual to meet with white specimens of that 

 bird. — C. D. Wolstenholme. 



Scarce Painted Lady. — It may be interesting 

 to your readers to know that I caught on the 2nd of 

 September, a good full-sized specimen of the scarce 

 "Painted hady" (Cynthia Hunter a), at Hayling Island, 

 Hampshire. I have not heard of the capture of this 

 rare butterfly in this district before. — H. W. L. 



Green Sandpiper. — It may interest some of the 

 readers of this paper to know that a friend of mine 

 shot on the 15th of August last, a fine specimen of 

 the Green Sandpiper (Tringa ochropus), near Wood- 

 bridge, in Suffolk. It perfectly answered to the 

 description given of it in Morris's "British Birds," 



