11 



now on a commercial basis. Prior to the establishment of the present 

 glass works, the German Government had made special grants of money to 

 Dr. Schott and Dr. Abbe, in furtherance of a large series of experiments 

 in the manufacture of optical glass, with the distinct purpose of promoting 

 scientific improvements in optical instruments. One of the principal aims 

 of the experiments had been to determine precisely within what range it 

 was possible to control the ratios of refraction and dispersion, utilising the 

 whole known series of substances capable of vitrification. Upwards of 1000 

 different samples of glass had been made, of which the chemical composition 

 and other technical ilata, as also the optical analysis, had been systematically 

 tabulated, and the experience thus gained was now available to meet the 

 demands for oi)tical glass of any required refractive and dispersive powers 

 within the limits under control. The importance of the aims in view could 

 hardly be overrated, for telescopes, field glasses, &c., microscopes and photo- 

 graphic lenses, all stood in need of a greater range of media to not only 

 lessen the difficulties of construction, but to further their advancement to 

 higher standards of excellence. The first important practical outcome of 

 Dr. Schott's experiments had been the production of the apochromatic 

 objectives, by Messrs. Zeiss, on computations made by Dr. Abbe. It was 

 also known that telescope object-glasses were in progress in which the higher 

 achromatism due to the new glass, was the essential aim. The progress 

 shown in the new microscope objectives clearly pointed to the possibility 

 of analogous improvement in photographic lenses, where an increased 

 facility of obtaining achromatism would certainly lead to larger and flatter 

 field with a given linear aperture and focal length— qualities of the highest 

 importance, which would not fail to be appreciated by every one interested 

 in photography. 



A cordial vote of thanks was conveyed to Mr. Mayall for his paper, 

 this being moved by the President, and seconded by Mr. A. ISToEirAX Tate. 



April lit.— The Rev. H. H. Higgins alluded to the discovery of a new Marine 

 Medusa, by a member of the Chester Society of Natural Science, as an 

 illustration of the value of early dredging work, the probability being that 

 the Marine Fauna of winter and early spring may materially ditler from that 

 of the summer. 



The paper of the evening was read by Mil. C. George Lee, M.R.C.S., 

 on the " Development, Structure, and Functions of the Ear." The 

 lecturer described the structure of the human ear, fully explaining all its 

 parts, and illustrated the same on the screen by means of the oxy-hydrogen 

 lantern, prepared specimens and models. After some discussion, in which 



