ZOOLOGY AND BOTANY, MIOKOSCOPY, ETC. 1021 



may be too black for it, and what we have to aim at is that mean which 

 will show the detail in one without making the other too glaring. 



Having made our arrangements according to what is here advanced, we 

 ought to be able to show the various minute organs of insects and the details 

 of vegetable and animal tissue. I have shown very finely the blowfly's 

 tongue over sixteen feet long, and the male flea with its outstretched legs 

 twelve feet long. Sections of spine of Echinus may be magnified to seven or 

 twelve feet diameter, and sections of a rat's tail eight feet diameter. Mites 

 in cheese with such powers become large as guinea-pigs, and Volvox globator 

 gracefully rolling over a sixteen-feet screen are larger than tennis-balls. 

 The cornea of the Dijtiscus is a most wonderful object when shown eight to 

 ten feet in diameter. 



When I say that such things can be shown in such enormous sizes, you 

 must not suppose that the display will be like an outline map, black and 

 skeleton-like in appearance upon a white ground. Instead of that the 

 small capillary blood-vessels in anatomical sections, the various appendages 

 of the feet of insects, the hairs of plants, the rings of insect tracheae, the 

 eyes of insects with the light gleaming through each facet of the cornea, 

 with other equally minute details, can be displayed to an audience with 

 very great satisfaction. That, you must admit, far surpasses anything ever 

 achieved by the old lantern Microscope, and we boldly challenge any 

 admirer of the old method to show that he is not now left as far behind by 

 the new one as the old stage-coach is left behind by the railway train. 



I think I ought to say that my lantern Microscope has been made by 

 myself. All its details have been worked out by myself. I have, of course, 

 utilized any old photographic lens mount, or old Microscope fittings which 

 I could get to work uj) into my arrangement, so as to save mechanical 

 labour. It fits, as you will see, into the ordinary lantern front. The alum 

 trough goes into the ^ilace which holds the slider when the lantern is used 

 for ordinary pictures. The stage is one of Dancer's old lantern Microscope 

 stages, but is modified so as to hold and enable me to change the substage 

 condensers, which can be done more easily and with less loss of time 

 through mine than it can be done through any other arrangement. The 

 compactness of the instrument is also something worth considering. 



Since the foregoing pages were written I have fitted up a 1-inch 

 objective which is very satisfactory. It transmits a large beam of light, 

 and gives a flat field of great size, the central and marginal definition 

 being fairly good at the same time. As a rule the best ordinary objectives 

 give no definition beyond a small circle in the middle of the field." 



Newton's Electric Polarizing Projection-Microscope. — This instru- 

 ment, constructed for the Science and Art Department, South Kensington, 

 by Messrs. Newton and Co., and exhibited at the Conversazione in 

 November, is of similar construction (with only necessary modifications) to 

 the oxyhydrogen projection Microscope which was described by Mr. L. 

 Wright in this Journal, 1885, p. 196. It will give good results with im- 

 mersion lenses up to 6000 diameters and upwards ; the magnification 

 possible depending chiefly upon the opacity of detail necessary for a large 

 screen image. 



In addition to the usual polarizing effects it is fitted with lenses for 

 exhibiting the brushes and coloured fringes in crystals, and also for use 

 with the oxyhydrogen jet. 



Lehrke's Lens-holder.* — Herr J. Lehrke's arrangement (fig. 211) 

 consists of a cylindrical metal- or horn-mounted lens, 2-4 cm. long, and 



* Zeitschr. f. Instrumentciik., vii. (1887) pp. 218-9 (4 figs.). 

 1887. 3 X 



