ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 355 



Further on he says, " These Microscopes are sometimes fitted up 

 with a toothed rack and pinion for the more ready adjustment of the 

 glasses to their proper focus." 



These two modifications constitute the principal differences between 

 the Bate Microscope and the one named after John Ellis, and used by 

 him in 1752-4 when preparing his work, An Essay towards a Natural 

 History of CorraJines. Ellis there says the Microscope was made by 

 Cuff, and he gives a figure and description. The figure was used by 

 Adams in his Essays, and on a reduced scale may be found in Dallinger's 

 edition of Carpenter on the Microscope. 



Cuff's Microscope is evidently the forerunner of many modern 

 dissecting Microscopes. 



The date of this (Bate) Microscope is doubtful, but there is reason 

 to believe that Bate's instruments were produced somewhere about the 

 early part of the last century. 



It scarcely requires any further description, beyond mentioning that 

 there are four lenses, the two higher powers being provided with 

 Lieberkiihns. 



Old Microscope by Plossl, of Vienna.— This Microscope, which was 

 exhibited at the Society's Meeting on January 20, and is represented in 

 fig. 56, resembles in general character the old Microscope by Schiek, 

 figured by Quekett in his Practical Treatise on the Use of the Microscope, 

 2nd ed. 1852, fig. 50, p. 102. 



It is an early example of a Continental Achromatic Microscope, and 

 its date may be given approximately as 1845. 



The brass body, 10J in. long, is supported on a short curved piece, 

 which slides on a triangular steel bar by rack-and-pinion movement. 

 The teeth of the rack are let in on the under surface of the steel bar, 

 and the latter is fixed by a compass joint to a solid, upright brass pillar, 

 which stands on a folding tripod with levelling screws at each end. 

 Three brass discs are provided, on which the sharp points of the levelling 

 screws rest. 



The stage is movable, for fine adjustment focussing, on the same 

 triangular bar by means of a fine screw fixed at the end of the bar. 

 Another screw at the back serves to clamp the stage in any position. 



The stage has mechanical motion in two directions ; a fine screw on 

 the right gives lateral motion to the extent of about | in. On the left 

 lower side a screw, acting on a lever, and with the stage plate pressing 

 against a spring at the top of the stage, gives up-and-down motion. A 

 horse-shoe shaped piece on the stage holds the object slide, and can be 

 lifted by pressing against a spring below the stage. 



In addition to these movements there is on the right side a large 

 drum micrometer screw, with divisions reading to 0*00001 of a Vienna 

 inch, and also some divisions on silver at the bottom of the stage. The 

 screw works against a spiral spring enclosed in a small brass cylinder on 

 the other side of the stage. 



The single mirror on a swivel, fixed to the steel bar, is concave, and 

 provided with blackened brass diaphragms to partly cover the mirror 

 when less light is desired. 



There are four Huyghenian eye-pieces and one large positive eye- 

 piece, having two large "plano-convex lenses, the convex sides turned 



