KNOWLEDGE & SCIENTIFIC NEWS. 



[August, 1905. 



C'jndlUtcd ilj F. SlllLLINGTON SCALES, I'.R.M.S. 



R^oyal Microscopica.1 Society. 



June 21st, at 20, Hanover Square, G. C. Karop, Esq., 

 M.R.C.S., Vice-President, in the chair. — Three old 

 microscopes were presented to the Society's collection 

 by Mr. C. L. Curties. A noteworthy donation to the 

 Library was the concluding: part of Dr. Braithwaite's 

 " British Moss Flora," the publication of which ex- 

 tended over 25 years. Dr. Lazarus-Barlow exhibited 

 and described a new form of warm stage, devised by 

 him, which could be heated by oil or gas. The regula- 

 tion depended upon the expansion and contraction of a 

 fixed volume of air, acting through a manometer upon 

 a delicately-balanced lever, at one end of which a silver 

 rod was carried in a horizontal position, the flame being 

 applied to one end of the silver rod, while the other 

 end, which was bent downwards, dipped into a parafBn 

 bath attached to the side of the stage. .As the tempera- 

 ture of the stage increased, the contained air expanded, 

 and acting on the manometer caused the lever to raise 

 the silver rod and so to practically withdraw the bent 

 portion from the paraffin bath. Mr. C. R. C. Lyster 

 also exhibited an improved form of warm stage, heated 

 by electricity. Such warm stages are generally heated 

 by resistance coils, but the variations in the intensity 

 of the ordinary house current render the temperature 

 variable, but Mr. Lyster found he could maintain a 

 perfectly even temperature by using cryptol as a resist- 

 ance, whilst the amount of current did not exceed 150 

 milamperes. Mr. C. L. Curties exhibited an arrange- 

 ment for obtaining dark ground illumination with high 

 powers by a stop over the objective, which was sug- 

 gested to him by a contrivance of Leitz. Mr. Curties 

 observed that only in certain cases were the images 

 of the markings on diatoms shown by this means to be 

 considered as trustworthy evidence of their real struc- 

 tures. Mr. Rheinberg called attention to an experi- 

 ment, showing that the appearance of a grating could 

 be produced in the field of the microscope without there 

 being anything on the stage. ITie lines seen were 

 achromatic interference bands, produced with the help 

 of two of Thorp's gratings of equal pitch placed behind 

 the objective. Mr. Rousselet called attention to a living 

 specimen of PlumaUlla punctata {Hancock), sent by Mr. 

 Hood, of Dundee, which has apparently not been 

 recorded in England since its discovery by Hancock 

 in 1850. It diflcrs from other species of Plumatella, 

 mainly in having a soft, transparent ectocyst. Mr. 

 Nelson communicated a note on the Tubercle Bacillus, 

 and Mr. A. E. Conrady gave a resumi of his second 

 paper on " Theories of Microscopic Vision." The pro- 

 ceedings concluded with an exhibition of fine zoological 

 lantern slides, lent by .Mr. .\. Flatters. 



The Qviekett Microscopical Club. 



The 423rd ordinary meeting was held on June 16th, at 

 20, Hanover Square, W., the I'resident, Dr. E. J. 

 Spitta, F.R.A.S., F.R.M.S., in the chair, 



Mr. \V. VVesch^, F.R.M.S., gave an abstract of his 



paper on "The Genitalia of Glossina palpal is," the 

 Tsetse fly, the host of the " sleeping sickness " 

 organism. This was shown to be homologous with 

 certain other flies, though differing in the presence of a 

 double le\er at the extremity of the central organ, a 

 feature which also occurs in the cockroach. 



Mr. Julius Rheinberg, F.R.M.S., showed an experi- 

 ment on the production of achromatic interference 

 bands in a new manner, which formed Ihc subject of 

 a paper which he had recently read at the Optical Con- 

 vention. Certain experiments in connection with the 

 theory of microscopic vision had led to the curious 

 result in question, which amounted in effect to pro- 

 ducing in the microscope, on the object stage of which 

 a piece of paper having a large perforation had been 

 placed, the appearance as if a grating had been placed 

 over it, the lines appearing perfectly sharp in black 

 and white. 



Mr. Rheinberg gave a description of the manner in 

 which this striking interference image was produced. 



Mr. Wesche then gave a popular lecture on " Pond 

 Life," which he hoped would encourage any novices 

 who might be present to take up this fascinating branch 

 of microscopy. It was illustrated by a number of 

 lantern slides prepared from Mr. W'esche's drawings 

 and designed to show the objects under dark ground 

 illumination. 



The next general meeting of the Club will be on 

 October 20th, but the usual fortnightly meetings will 

 be held during the vacation for gossip and exhibition 

 of objects. There are also several excursions during 

 the summer months to various collecting grounds. 

 \'isitors will be welcomed to both meetings and excur- 

 sions, and may obtain full particulars on application 

 to the Hon. Secretary, Mr. A. Earland, 31, Denmark 

 Street, Watford. 



Home-Made Dissecting Staind. 



I HAVE been several times asked to recommend a dis- 

 secting stand, and though for convenience the stands 

 made by Zeiss, Leitz, and Reichert in various patterns 

 cannot well be improved upon, still the cheapest of 

 them costs, with two lenses, a couple of sovereigns, and 



it may interest many of my readers if 1 describe here 

 a stand which can be made at home by anyone who can 

 do a little carpentering and which need cost only a few 

 shillings. A reference to the accompanying drawings 

 is almost .self-explanatory. The total length of the 

 stand should be about 14 inches, and the width about 



