836 PROCEEDINGS OF THE SOCIETY. 



Lethbridge, combining Telescope and Microscope, which could be used 

 alternately by unscrewing the eyepiece of the telescope and screwing it 

 on to a drum Microscope stand. The name inscribed on the apparatus 

 was that of Charles Nephew & Co., of Calcutta. 



Dr. Spitta, in returning thanks to Mr. Rousselet for his interesting 

 exhibition, asked whether he might suggest that the Society should, if 

 possible, try to induce Mr. Rousselet to commit his valuable knowledge 

 in regard to the history of Microscopes to paper. Such a history was, 

 he believed, nowhere to be found, and he would venture to say that 

 none possessed so intimate an acquaintance with the subject as Mr. 

 Rousselet. It seemed a pity, he thought, that they as a Society 

 supposed to represent Microscopy should not possess some such a 

 history to which reference could be made when necessary. 



The President replied that he thought it would be an excellent thing 

 if Mr. Rousselet would fall in with Dr. Spitta's suggestion, and he was 

 sure that all present were of the same opinion. Moreover, the fact that 

 the collection of Microscopes in their possession was about to be put into 

 better keeping and condition would, he thought, afford an excellent 

 excuse for the compilation of a book such as that suggested, and would 

 at the same time furnish a description of the instruments, which such 

 rearrangement would make necessary. He hoped Mr. Rousselet would 

 be persuaded to undertake this work. 



Dr. Spitta remarked that after such an invitation Mr. Rousselet 

 could hardly refuse ! 



Mr. Rousselet replied that he was afraid it was too big an order. 



Mr. Barnard read a paper on "A Geometric Slide Photomicrographs 

 Apparatus," the principles of which he illustrated by a diagram and by 

 drawings on the blackboard. The apparatus itself was exhibited. 



In the course of his explanation, Mr. Barnard said that the apparatus 

 was designed on the principle of the geometric slide throughout, as 

 enunciated by Lord Kelvin and Tate. The geometric clamp was intro- 

 duced in a modified form only, but was of such interest that a short de- 

 scription would not, he thought, be out of place. In the photomicro- 

 graphic apparatus shown, an attempt had been made to embody the 

 principles of a geometric slide throughout. Apart from that the design 

 was such that extreme rigidity was obtained, and there was little or no 

 liability of alteration of any of the components as the result of 

 climatic influences. Owing to this rigidity the whole apparatus would 

 move together if subjected to any shock or vibration. The base of the 

 apparatus was made from two castings which were designed on the girder 

 principle. Each of these might be resolved into a triangle so that the 

 utmost stiffness was obtained. The two castings were braced together at 

 each end and in the middle by a small cast piece. 



The portion to carry the Microscope was also on a pair of castings, 

 these being triangular iu shape, and braced together in the same way as 

 bhe main castings. The former pair of castings was supported at the end 

 away from the camera on a metal cone, which allowed them to be swung 

 out from the central position. The female part of the cone was on the 



