PROCEEDINGS OF THE SOCIETY. 851 



the use of such objectives was likely to be restricted, owing to the price, 

 which was 10,000 fr. or 4.001. 



Mr. T. Powell, in reply to a question as to the possibility of pro- 

 ducing such an aperture, said it would be quite possible to make it with 

 such a medium as the immersion fluid named, that was, of course, 

 supposing its refractive index was as high as 1-6. 



Mr. Ingpen said that the refractive index of this medium was 1 • 8. 



Mr. Crisp said that it would be remembered that some time ago an 

 extraordinary description was read at one of their meetings from the 

 Proceedings of the American Association for the Advancement of 

 Science, a society having the same object as our British Association, 

 in whicla it was proposed to convert a Microscope into a microtome by 

 placing the imbedded substance in the lower end of the tube and 

 cutting sections by means of a blade fitted to move upon the stage-plate, 

 the material being moved forward by the action of the fine-adjustment. 

 He had now brought the apparatus described for exhibition, as it might 

 well be thought that the original account was written as a joke, and 

 that it could not be seriously put forward. Having fitted up the con- 

 trivance in the manner described, he showed the way in which it was 

 proposed to be used. 



Mr. Karop and Mr. J. Mayall, jun., made several suggestions as to 

 possible conversions of a Microscope to domestic and other uses if it 

 was not considered necessary to confine it to its original purpose. 



Mr. J. Mayall, jun., described the various Microscopes and acces- 

 sories which he had examined at the Paris Exhibition, pointing out that 

 whereas at former international exhibitions most of the best makers in 

 England, America, and other countries, were exhibitors, on this last occa- 

 sion they had been rather conspicuous by their absence. He had seen very 

 little that was new in the matter of design. The French opticians were 

 fairly well represented as to numbers, but the instruments they exhibited 

 were for the most part of the old, not to say antiquated types. Where, 

 perchance, one or another had ventured to add an adjustable substage 

 to his Microscope, this had been done in what English microscopists 

 would regard as a clumsy and ineffective way, by no means up to the 

 standard that would be required in England. When French opticians 

 were questioned why they did not produce Microscopes more suitable 

 for the critical microscopy of the present day, they re])lied tliat there 

 was no amateur scientific class in France as in England, and that they 

 were therefore obliged to restrict themselves to what was suitable for 

 medical use ; that medical students there used the Microscopes very 

 roughly, and the instruments had consequently to be made strong and 

 heavy, without much regard to delicacy of adjustment. Comparing 

 the I'rench exhibits with those of previous exhibitions, he thought the 

 advance shown was i^rincipally in the direction of finer lacquering or 

 nickelizing, or more elaborate upholstery. Here and there ingenuity 

 was shown in packing a portable Microscope in a very small space, or 

 in making a large number of appliances fit into dainty-looking velvet- 

 lined partitions, so that the eye at least was pleased ; but the solid 

 merits of construction and design, as evidenced by good mechanism 

 giving the microscopist perfect command of all necessary adjustments. 



