>8o 



SCIENCE-GOSSIP. 



even if makers can be persuaded to adopt its some- 

 what various suggestions. The resolutions arrived at 

 by the Council on December 20 last were : that the 

 standards adopted by the Council in 1882 be with- 

 drawn ; that the standard size for the inside diameter 

 ( >f the sub-stage fitting be 1-527 inches (38 786 mm.) ; 

 that the gauges for standardising eye-pieces be the in- 

 ternal diameters of the draw-tubes, the tightness of the 

 fit being left to the discretion of the manufacturers. 

 Further, that the following four sizes of the internal 

 diameters of the draw-tubes be adopted : — R. M. S. 

 No. 1, -9173 inch (23-300 mm.); R. M. S. No. 2, 

 1-04 inches (26-416 mm.); R. M. S. No. 3, 1-27 

 inches (32-258 mm.); R. M. S. No 4, 1-41 inches 

 (35-814 mm.) ; and that plug and ring gauges of all 

 the above sizes be kept in the Society's rooms ; also 

 that the public, on payment of a small fee, be allowed 

 to inspect them. The size of the sub-stage is that 

 now in fairly general use amongst English makers, 

 the variations being not more than a few thousandths 

 of an inch. The sizes of the eye-pieces are arrived 

 at as follows : — No. 1 is the Continental gauge ; it is 

 in general use on the Continent, and has been adopted 

 by several of our English makers for their students' 

 size instrument. No. 2 is the mean of the sizes used 

 by the English trade for students' and small micro- 

 scopes, and is apparently meant to meet the objec- 

 tions of those makers who have hitherto clung 

 tenaciously to their own originally adopted sizes. 

 No. 3 is the mean of the sizes used for medium-sized 

 binoculars and other microscopes of a similar class, 

 and is apparently also an attempt to meet the 

 objections of those makers who have hitherto de- 

 clined or been unable to adopt the Society's standard. 

 The standard adopted by the Society for this eye- 

 piece was formerly 1-35 inches, and therefore those 

 makers who fell into line and adopted this size 

 will now have to alter everything— which seems to 

 us a somewhat ungrateful return for their loyalty, and 

 likely to inconvenience equally those who already 

 possess microscopes made to the old standards. Size 

 No. 4 is, we think, that adopted by Messrs. Powell 

 & Lealand alone, and is not likely to become general, 

 as it is too large for most instruments. We cannot 

 help thinking that two standard sizes only would 

 have been better — the Continental size for students' 

 instruments, and No. 3 size for large instruments. 

 However, we are grateful for any advance in the 

 direction of uniformity, and earnestly trust that all 

 our leading makers will now adopt these standards. 

 Buyers of microscopes could materially assist by 

 insisting on their microscopes being made in accord- 

 ance with the Society's standards. We may add 

 that the standardisation of the eye-piece cap, and 

 apparatus to be used above the eye-piece, will follow 

 shortly. 



ANSWERS TO CORRESPONDENTS. 



W. C. B. (Appleby).— You will find the points on 

 which you ask for information fully explained in the issue 

 of March last of SCIENCE-GOSSIP, under the heading 

 of " Microscopy for Beginners." where microscope 

 manipulation is dealt with. With regard to dark 

 ground illumination, we may simply say in the mean- 

 time that the size of the stop must be proportioned to 

 the aperture of the objective ; the higher the aperture 

 the larger the stop. Try making various stops for 

 yourself out of blackened cardboard. We are glad 

 you find our columns so helpful, and we are always 

 pleased to answer questions. 



MICROSCOPY FOR BEGINNERS. 



By F. Shillington Scales, F.R.M.S. 

 {Continued from page 249.) 



Dissecting can be done with the simplest appara- 

 tus, but some form of dissecting microscope or stand 

 is a great convenience, and an actual necessity where 

 much or prolonged work is done. The microscope 

 itself can be used together with the lowest-power 

 objective, but in this case the image will of course be 

 inverted, unless what is billed an " erecting lens " be 

 used. To protect the stage, Mr. West's table stage, 

 described and figured in Science Gossip, Vol. VI., 

 N.S., page 30, is a most simple and practical device ; 

 it is provided with hand-rests, and can be used also 

 as a mounting-table. There are, of course, different 

 types of dissecting-stands made by the opticians, of 

 which, perhaps, the cheapest is Leitz's small dissecting 

 microscope, sold at 20s. without lenses. As we are 

 writing primarily, however, for those who want to 

 economise as much as possible, we illustrate here a 

 small stand that can be made at home by any one 

 able to use his hands, and that will cost but a 

 few shillings. The design itself is not original, as 



Fig. 1. Home-made Dissecting-stand. 



a similar but more elaborated stand is figured in 

 opticians' catalogues at two guineas and upwards. 

 The drawings almost explain themselves. The total 

 length should be about 14 inches, and the width 

 about 4 inches. The sloping rests for the hands 

 might be, say, 2 inches high at the lowest ends, and 

 4 inches at the highest. This latter measurement, 

 however, should be governed by the size of the mirror, 

 which must have ample room to swing. The mirror 

 itself is a simple penny mirror such as can be bought 

 at any toy-shop, and it is let into a piece of wood 

 which swings on wooden or metal pivots between 

 the two centre uprights. This piece of wood could 

 be hinged to the bottom of the stand instead ; but in 

 that case the mirror would not remain central when 

 lifted at an angle. A little more skill would be 

 required to arrange universal movements. The stage 

 is a piece of plate-glass 5 inches x 4 inches, ground 

 at the edges, and can be ordered at any glazier's. It 

 lifts out, if necessary. Two pieces of cardboard of 

 the same size should be cut to go underneath when 

 required ; both should be covered with black paper, 

 and one should have a hole about I finches in dia- 

 meter in the centre. The whole stand might be 

 made of wood § inch thick, mahogany being prefer- 

 able to pine, and the dovetailing or grooving should 

 be finished as carefully as possible. 



The holder for the lenses can be made, as illus- 

 trated, by fitting a piece of {-inch brass tube about 

 8 inches high into a small stand, say, i\ inches 

 in diameter. A piece of springy ^-inch brass wire is 

 then rolled several times tightly round the upright as 

 shown ; one end is turned up about 3 inches away 

 from the stand, and the other end is shaped into a 

 ring to hold a watchmaker's eye-glass. This last can 

 be bought anywhere for iod. or is., and makes a 



