THE PRESIDENT'S ADDRESS. 121 



working within the female screw cut in the body of the instrument, 

 served to get the focus, the various magnifying powers being 

 screwed into the end of the body. A handle, fastened by a screw 

 to the outside of this tube, served to hold this microscope up to the 

 light in examining an object. This, after all previous contrivances, 

 was deemed a great advancement in adaptation of focus and con- 

 venience of application to objects ; but soon the inventive genius of 

 that day found means for its improvement, and it was followed by 

 the single reflecting microscope, for it was found to be inconvenient 

 to hold Wilson's microscope up to the influence of direct light; 

 therefore a modified arrangement of it was supported by a vertical 

 scroll fixed in a circular wooden foot, and a mirror mounted beneath, 

 so arranged that ligbt from any source could be directed into the 

 body of the microscope. We have here, in this instance, the first 

 practical inception of our present arrangements, and although this 

 was considered another step in advance of Wilson it did not satisfy 

 the growing needs of microscopists of that day, inasmuch as it 

 could only be used for transparent objects, and they needed some- 

 times to look at those which were opaque, and condensing lenses 

 were then added to this form of microscope. Culpepper, and after 

 him Cuff, still further improved upon this, till a great advance 

 towards our present form was made by Benjamin Martin in an 

 instrument designed to serve the combined uses of what at that 

 time were divided into single, compound, opaque, and aquatic 

 microscopes. It would be tedious were I to enlarge upon the 

 progressive stages by which our grand instruments of to-day have 

 been undergoing a gradual process of evolution from the primitive 

 and ere-while considered perfect instrument of 140 years ago, and 

 therefore I must omit what is so well known to all present. 



Although the principle of binocular vision was applied to tele- 

 scopes by John Lippersheim for the Dutch government in 1609, it 

 was not till 1667 that it was applied to the microscope by Pere- 

 Cherubin, of Orleans. Although the clever friar was so successful 

 that the effects were stated to be marvellous and surprising, yet the 

 discovery laid dormant till Sir Charles Wheatstone directed the 

 attention of the scientific public to his stereoscope, and, calling in 

 the aid of our distinguished opticians, Messrs. Powell and Ross, 

 tried to construct a microscope on stereoscopic principles ; but prac- 

 tical difficulties opposed further progress in this direction. 



In 1851 the difficulty was solved by Professor Riddle, of the 



