156 Transactions of the Society. 



(Optics, Part II.).* " Single " is found for the last time in Potter's 

 Optics, Part 1., 1847. 



" Opaque " is meant to convey the information that lieber- 

 kuhns (invented 1738), are supplied for the illumination of opaque 

 objects. The term "Aquatic " requires a longer explanation. In 

 1755 Cuff made Ellis's Aquatic Microscope, or what would now 

 be called a dissecting stand. The lens-holder was so mounted that 

 the lens could be moved backwards and forwards, as well as in 

 arc, over an object upon the stage. This movement of the lens 

 over the object, instead of the object under the lens, was at that 

 time thought a great deal of because it was said that aquatic 

 animals were disturbed by the movement of the stage. These 

 movements were still in use in 1852, for they are seen in a dis- 

 secting stand by And w . Eoss. f All Microscopes having these 

 movements were said to be " aquatic." 



Martin's super-stage, found in numerous models of that time, 

 consists of a plate of brass with three holes in it, the centre one 

 1\ in., and those on either side "7 in. in diameter. There was a 

 pivot on the lower side which fitted into a hole in the stage, 

 permitting the plate to be moved in arc. A watch-glass for 

 holding living animals in water was placed in the large central 

 aperture, and a piece of plain glass in one of the side holes for 

 holding objects suitable for examination by transmitted light ; in 

 the other hole was fitted a piece of ivory, black upon one side and 

 white upon the other, for holding objects which were to be 

 illuminated by a lieberkuhn ; a white object would be placed upon 

 the black side of the disk, and a black object upon the white side. 

 So Martin's super-stage was an ingenious and useful adjunct to 

 Microscopes of that date. 



The total height of this Microscope was 14 in., the body 

 being 6 in. when the draw-tube was closed. These are the same 

 dimensions of Benjamin Martin's " No. 1," which is illustrated on 

 page 474, fig. 81, of this Journal, 1898. 



From Watkins' and Gregory's Microscopes was evolved, in 

 1798, Jones's % " Most Improved," which is, in essential particulars, 

 the form of the modern Microscope. Jones's " Most Improved " 

 has a foot with an upright pillar, to the top of which is hinged, by 

 a compass joint, a limb which carries the magnifying portion, the 

 object and the illuminating apparatus, and this is the form of every 

 Microscope at present in use, for if we examine the most aberrant 

 form, viz. Powell's No. 1, we find a gipsy tripod foot, which is 

 merely a foot and pillar in one piece ; the bent claw obviously falls 

 under the same category. 



* Barlow, Ency. Metrop., art. Optics. " Simple is found in the index, but the 

 word in the text is " single." (Accompanying plate is dated 1822.) 



f Quekett on the Microscope, 2nd ed., p. 59, fig. 37; copied in this Journal, 

 1900, p. 428, fig. 109. J W. and S. Jones, 135 next Furnival's Inn, Holborn. 



