1899] THE ROYAL SOCIETY'S CONVERSAZIONE 42 5 



The Royal Society's Conversazione. 



The first of the two annual conversaziones of the Royal Society was 

 held on May 3. Among the exhibits of special interest to our readers 

 the following may be recorded : — 



The tsetze fly committee of the Royal Society exhibited enlarged 

 photographs, taken by Surgeon-Major Bruce, illustrating districts in 

 South Africa affected by the tsetze fly disease. 



Prof. J. Norman Collie showed some fine photographs taken during 

 a journey of exploration to the sources of the Athabasca and 

 Saskatchewan rivers. The chief result of the expedition was the 

 discovery of the largest snow-fields and highest peaks at present 

 known to exist in the Canadian Rocky Mountains. 



Mr. Saville-Kent showed some lantern slides of various zoological 

 and botanical subjects reproduced in their natural colours by photo- 

 graphy, prepared from negatives taken through screens corresponding 

 in tint with the three primary colours of the spectrum — red, green, 

 and blue- violet — as first suggested by the late Prof. Clerk Maxwell, 

 and since adopted in the colour-photography researches and inventions 

 with which the names of Ives, Joly, Lippmann, Lumiere, and others are 

 associated. The positives from the foregoing negatives are printed as 

 three-film or glass transparencies, each of which is tinted with the 

 colour complementary to that of its respective negative ; they are then 

 superimposed in correct register. 



Messrs. J. E. Barnard and T. A. B. Carver demonstrated an 

 elaborate photomicrographic apparatus for high powers, designed for 

 the Jenner Institute of Preventive Medicine. To secure rigidity 

 among the several components the apparatus is upon a stiff girder ; 

 which, in extreme cases, may be suspended by springs to isolate it 

 from a source of vibration. The apparatus is arranged for use with 

 transmitted light, but the illumination of opaque objects is provided 

 for by a prism carried upon a jointed support above the stage, the arc 

 lamp and condenser having sufficient range to allow the beam to be 

 thrown in a line parallel to and above the line of collimation of the 

 microscope. A useful feature is the graduation of the slides upon 

 which the components move ; thus the conditions under which any 

 photograph is obtained may be recorded and reproduced. The length 

 and rigidity of the apparatus permit of very great magnification with- 

 out blurring. Valuable results have already been obtained with this, 

 especially when aided by the differentiating action of monochromatic 

 illumination. 



At an adjoining table were to be seen numerous microscopic 

 preparations of mosquitoes, exhibited by Dr. P. Manson and Surgeon- 

 Major Ross, to show the development of the malarial parasites, Filaria 

 nocturna and Protcosoma grassii. 



