140 THE HISTORY AND DEVELOPMENT OF THE MICROSCOPE 



the eye being placed behind in the direction D at any point the 

 single lens or a combination might require. 



Culpeper and Seal-let's microscope requires a note, and is illus- 

 trated in fig. 108. It was inappropriately designated a ' reflecting ' 

 microscope, but this arose merely from the fact that it was the first 

 English model which employed an illuminating mirror. It was, 

 however, a dioptric, not a catoptric instrument, and is figured in 

 Dr. Smith's ' Opticks,' 1738. 



' A Pocket Reflecting Microscope ' was figured by Benjamin 

 Martin in his ' Micrographia Nova' in 1742, having the interesting 

 feature of a micrometer eye-piece depending on a screw with a certain 

 number of threads to the inch, and by which accurate measurements 

 could be taken. It was called a reflecting microscope because it had 

 a mirror fitted into its cylindrical base; but it was, in reality, a 

 compound refracting form, and appears to have a good claim to have 



been the original from w r hence the 

 modern 'drum' microscopes were 

 taken. 



Wilson devised a simple 

 ' screw-barrel ' microscope in 1702, 

 and Baker describes and figures 

 in 1742 the Wilson model 

 mounted on a scroll standard and 

 with a mirror mounted on the l>a-e 

 in a line with the optic axis. I-':,-'. 

 109 reproduces the drawing of 

 Adams. 



But Martin originated a lai-^e 

 number of improvements both in 

 the optical arrangements and the 

 mechanism of the microscope, and 

 was an excellent maker. He ap- 

 plied rack-and-pinion focussing ad- 

 justments, to the compound micro- 

 scope he added inclining move- 

 ments to the pillar carrying the 

 stage and mirror, and he furnished 

 the stage with rectangular movements. 



It was to this maker that the late Professor Quekett was 

 indebted for an early microscope, of which he evidently to the last 

 thought highly, and which was subsequently purchased by the Royal 

 Microscopical Society. A drawing of this instrument is given in fig. 

 110, and should be described in Quekett's own words. He says: 

 ' It stands about two feet in height, and is supported on a tripod 

 base, A; the central part or stem, B, is of triangular figure, having 

 a rack at the back, upon which the stage, 0, and frame, D, support- 

 ing the mirror, E, are capable of being moved up or down. The 

 compound body, F, is three inches in diameter ; it is composed of 

 two tvibes, the inner of which contains the eye-piece, arid can be 

 raised or depressed by rack and pinion, so as to increase or diminish 

 the magnifying power. At the base of the triangular bar is a cradle 



FIG. 109. Wilson's simple microscope 

 on scroll standard (as made by 

 Adams, 1746). 



