HARDWICKE'S SCIENCE- G OS SIP. 



39 



Slides made of wood are lighter and stronger than 

 glass ones, and look quite as elegant if made of 

 ornamental wood and polished, or covered with fancy 

 papers. In the first place, procure some thin boards, 

 about one-sixth or one-eighth part of an inch thick ; 

 these should be cut up into strips three inches long 

 and one inch wide, and ground smooth with sandpaper. 

 In the centre of these slips burn a hole to the required 

 depth by means of a heated iron rod. I consider that 

 this is a rery good way of making a cell in the wood, 

 as it leaves the surface black, and if the iron is 

 carefully used it makes the bottom of the cell 

 beautifully even. Into this cell drop a little thin 

 liquid glue (which is made of shellac dissolved in 

 methylated spirit), and with a small brush spread it 

 all over the interior of the cell, and some little 

 distance round the margin. This process has the 

 very desirable effect of rendering the cell damp proof. 

 For small objects a circular piece of black or dark 

 coloured paper should be glued in the bottom of the 

 cell, and the object (carefully dried) should be stuck 

 in the centre of the paper disc ; if, however, the leaf 

 with fungi has been cut sufficiently large to fill the 

 bottom of the cell the paper circle may be dispensed 

 with altogether. After another process of drying the 

 thin glass cover may be affixed by means of any of 

 the various cements. The slide may now be finished 

 in the ordinary way of glass slides by means of a ring 

 or two of sealing-wax varnish, or by pasting a piece 

 of ornamental paper ij inch long and I inch wide 

 (with a hole of the same size as the cell previously 

 punched out) over the slide. Nothing now remains 

 to be done but to write the label and gum it to the 

 slide. I venture to think that this method will be 

 found to be equal, if not in some respects superior, to 

 others in which the cell is built up on the slide, as 

 there is no danger of the cell breaking off when 

 roughly handled. To many of the readers of these 

 remarks the method I have described may not be new, 

 and I believe wooden slides are often used for dry 

 objects by many workers, but to those who have not 

 yet given it a trial, and especially to those who make 

 a special study of that delightful 

 branch of micro-botany, micro- 

 fungi, I hope it will commend it- 

 self as a thoroughly efficient and 

 simple method. — George Clinch. 



Cheap Polariscope. — "Eco- 

 nomy" in January number inquires 

 about a cheap polariscope. Years 

 ago I made one as follows, which 

 was as efficient as the prisms I 

 have used latterly. I took one 

 dozen oval pieces of crown glass 

 — thin covering glass — and fixed 

 them at an angle of about 56 in a 

 tin tube, which I made to spring into the stage aperture. 

 Another similar tube of glasses slid to the bottom of the 



Fig. 34— Cheap 

 polariscope. 



draw tube of the microscope. The polariserwas thus- 

 fixed in one position, and I rotated the draw tube to- 

 vary the effects obtained. A few pieces of mica served 

 instead of selenite. Obviously paper tubes could 

 be easily made, and would do perfectly. I append 

 sketch of tube of glasses, and think "Economy" 

 will have no difficulty in producing an efficient instru- 

 ment. If he has, I will give more instructions, or if 

 he has any difficulty with the theory of polarisation 

 I will try to clear it up for him. — Edwin Holmes. 



Cheap Polariscope. — "Economy" will find a 

 full description how to construct a make-shift polari- 

 scope in Dr. Lankester's "Half-hours with the 

 Microscope." If he has not got this book, I shall be 

 happy to send him a copy of the description. — E. 

 Clover, Sudbury. 



Steinheil's New^ Combined Achromatic 

 Triplet Magnifying Lenses. — We have used one 

 of these capital lenses, which are constructed so as to- 

 be used at a great focal distance from the object. 

 They are "aplanatic," and give wonderful definitions 

 over the whole field, even to such an extent that they 

 may be tilted to almost any angle without distortion.. 

 Consequently the highest powers may be used with 

 the greatest ease. They are conveniently mounted 

 in brass, as shown in the drawing, or in horn setting,. 



F'g- 35. — New Achromatic Lens. 



or tortoiseshell frame, and are intended for pocket 

 use. The linear magnifying powers are about $'-„ S, 

 12, 16, and 24 times, the equivalent focus being i'jj, IjL, 

 ]l, \, and I inch respectively. For all microscopic 

 examinations we regard them as the most perfect and 

 useful pocket lenses that have yet been introduced 

 either in this country or abroad. The drawing repre- 

 sents the exact size of the 1^ inch focus. The sole 

 agents for these useful lenses are Murray & Heath, 

 69 Jermyn Street, S.W. 



The Bittern in Kent. — It may interest some of 

 your ornithological readers to know that a fine bittern 

 {Botanrus stellaris) was shot in our marshes on the 

 24th November. It was flushed from a little stream 

 close to a brickfield by a bargeman, who was walking 

 for snipe. I believe it has been a stranger to our 

 locality for a long time, and there is every prospect 

 of its being one. — Roland Green, Rainham, Kent. 



