PROCEEDINGS OF THE SOCIETY. 413 



depressed l)y rack-and-pinion. The compound body can be removed 

 and replaced by a simple Microscope ; the stage also can be removed and 

 replaced. Provision is made for holding and illuminating living objects 

 and large opaque specimens. This Microscope is fully described in the 

 Transactions of the R.M.S. of 1862, p. 31. 



9. Gregory and AVright. (R.M.S. Cat. No. no.) Type— Alter- 

 natively Simple or Compound, uncorrected. The makers of this instru- 

 ment were siiccessors to Benjamin Martin. They follow his lead by 

 making the stem inclinable by a joint at its base. The body is attached 

 to a movable arm, which, in turn, is carried by the stem. This arm 

 can be swung about the axis of the stem, and moved to and fro in its 

 socket, these movements facilitating the exploration of a large specimen. 

 Focussing is effected by rack-and-pinion, which move ^he stem and body, 

 whilst the stage is fixed. This Microscope has a rotating multiple lens- 

 carrier nose-piece, invented by Pere Cherubini d'Orleans. 



10. Shuttleavorth. 1786. (R.M.S. Cat. No. 179.) Type- 

 Alternatively Simple or Compound, uncorrected. The stand of this 

 instrument is a somewhat later imitation of the Benjamin Martin type. 

 The triangular stem has a compass-joint at its base, by means of which 

 the whole' Microscope is inclinable. The stage has rack-and-pinion 

 focussing movement. The body is fixed to a movable and rotating arm, 

 and carries Francis Watkins' rotating multiple lens-carrier nose-piece. 

 The mirror and condensing lens slide on the triangular pillar. For 

 description, see Journ. R.M.S.. 1908, p. 365. 



11. Jones. 1798. (R.M.S. Cat. No. 51.) Type— Alternatively 

 Simple or Compound, uncorrected. This model follows an earlier form 

 of Francis Watkins, inasmuch as the compass-joint making the Micro- 

 scope inclinable is raised to the top of an upright stem, fixed to a tripod 

 folding foot. To the joint is fixed a square limb, on the top ot which 

 a short arm, movable by rack-and-pinion, supports the body of the 

 Microscope. The stage moves on the limb l)y rack-and-pinion, which 

 serves for the focussing of the object. The mirror and condensing-lens 

 slide on the same square limb. The object-glasses are contained in a 

 rotating multiple lens-carrier nose-piece. 



12. Cuthbert's Reflecting Microscope. About 1827. (R.M.S. 

 Cat. No. 12.) Type— Compound : Catoptric. The maker of this Micro- 

 scope attempted to produce achromatism by means of mirrors, carrying 

 into effect a suggestion originally made by Newton. The magnification 

 of objects is here effected by means of very small reflecting specula, and 

 the result for low and medium powers was very fairly satisfactory. 

 The body is fixed by a compass-joint on the top of the telescopic stem 

 supported on a folding tripod. The focussing is effected by moving the 

 stage, and the latter has rectangular motion. 



13. Hugh Powell. 1839. (R.M.S. Cat. No. 128.) Type- 

 Compound : Achromatic. This Microscope embodies new features which 

 have now been very generally adopted. The body, stage, and mirror 

 are carried by the limb, which itself is attached by a compass-joint to 

 an upright telescopic pillar raised on a solid tripod. The coarse- 

 adjustment by rack-and-pinion for the first time moves the body of the 

 Microscope, but the fine-adjustment is applied to the stage by a wedge 

 acted on by a micrometer screw. In this model also Hugh Powell 



