Notes. 591 



■earliest Compound Microscope that has its mirror attached to the 

 limb. 



In fixing the date of this Microscope we can assume that it is 

 an instrument made by an amateur on the lines of some model 

 before him. Now the Microscope he has evidently copied is that 

 ■of Benjamin Martin (1760-1770) * ; a signed and numbered (No. 1) 

 ■example of which is in my possession. 



It probably is not older than 1715, the date of the introduction 

 of the mirror, neither earlier than 1760-1770, because its object- 

 glass has a back lens ; but, evidently, it is an old instrument 

 made in the latter half of the eighteenth century. I have much 

 pleasure in offering this instrument to the Society for its acceptance. 



An Improved Horseshoe Stage. 



By Edward M. Nelson. 



"While working with a high power on a Microscope with a plain 

 stage, having only a circular hole in it, great inconvenience was 

 experienced in tilting the slide on its edge, for the purpose of feeling 

 the working distance, when bringing the lens into focus ; it there- 

 fore occurred to me that it would be a good plan to cut away all 

 the brass in front of the circular hole and make what is now known 

 as a " horseshoe stage." So in 1880, 1 asked Powell to cut out the 

 stage of his iron Microscope f for me. The advantage was at once 

 so apparent that I had three other instruments treated in the same 

 rnanner.J 



This form of stage is now largely used. Although the advan- 

 tage of this form of stage when ordinary slides are being examined 

 is obvious, yet some objection may be raised when dishes and 

 watch-glasses with convex bottoms are placed upon it, because of 

 their liability to slide forward in the horseshoe opening. I have 

 therefore designed this simple modification which will render this 

 form of stage suitable for all purposes. 



A flat plate of brass with a circular hole in it, having tongues 

 at the edges to slide in grooves cut to receive them, is pushed into 

 the horseshoe opening, when dishes, etc. are required to be placed 

 upon the stage. When ordinary slides are to be examined the 

 brass plate is withdrawn, and the horseshoe stage is left in its 

 •original condition. 



* Journ. E.M.S., 1S9S, p. 474, fig. 81. 



t Idem, 1899, pp. 209, 210, fi"'s. 44 and 45, and 1900, pp. 289-291. 



X Idem, 1883, p. 5.14, fig. 94; and 1887, p. 293, fig. 41, and p. 1013, figs. 238 and 

 239. 



2 Q 2 



