ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 367 



moves up and down with the stage. Numbers 1-6 are engraved on one 

 side of the limb to indicate the position of the stage with the six 

 objectives. The body of the Microscope is fixed to an arm which can 

 be moved backwards and forwards and also in arc over the object, and 

 carries Martin's multiple disk of object-cases. Below the stage a con- 

 densing lens is fixed on a separate arm, and made movable out of the 

 way by means of a joint when not wanted. The mirror is plane and 

 concave, and both the arms carrying the mirror and the condensing lens 

 are made to slide on the limb. 



The date of the present instrument may be given as about 1786. It 

 represents an important link between Benjamin Martin of 1782 and 

 Jones' " Most Improved " model of 1797, and as such it is a valuable 

 addition to our collection of old Microscopes. 



Leitz' New Penological Microscope, Type A.* — CI. Lincio, of 

 Varzo, fully describes this Microscope, of which Figs 87 and 88 give 

 side views. It is made with a heavy foot F (fig. 87) surmounted by a 

 forked piece S t, within which the upper body T may be inclined about 

 a hinge CI. The latter is situated on a level with the stage, at such a 

 height that when tilted back the Microscope may, without sacrifice of 

 stability, be made to receive the light direct from an artificial source. 

 The upper body is so designed as to provide an unusually large working 

 space in the plane of the stage, and, incidentally, forms a convenient 

 handle by which the Microscope may be grasped. This part carries the 

 mechanism for the coarse-adjustment g E and the fine-adjustment /E. 

 The former is effected by a rack-and-pinion provided with obliquely cut 

 teeth so as to minimise play. The range of motion is such that a 

 working distance of 9 • 5 cm. is obtainable with the shortest (low-power) 

 objective (No. 1), and 7 ' 5 cm. with the largest (high-power) objectives. 

 The fine-adjustment is of the new form which has been already described 

 in this Journal. f The stage-plate is provided with holes for the insertion 

 of object-clips and angular-stops. The graduations and angular-stops 

 serve as finders. The thickness of the stage-plate suffices, moreover, for 

 the adaptation of fixing-clamps and clips for the usual forms of stage- 

 fittings, rotation devices, etc. The position of large objects may, after 

 centring the stage and setting the index back to the respective numbers 

 of the h mm. scales, be recorded with the aid of the graduations along 

 two radial lines engraved at right angles to each other upon the stage- 

 top. As a matter of fact an object marker, which screws to the tube 

 like an ordinary objective, is obtainable for an insignificant sum, and is 

 much to be preferred to any of these finders when quick work has to be 

 done and when it is intended to subsequently photograph selected 

 portions of specimens. The stage is fitted with a clamp and fine-adjust- 

 ment, which will be found a useful adjunct in the measurement of angles 

 of crystals, in determining the direction of extinction, etc. It consists 

 of a tangential screw with milled head T S (fig. 88), which engages into 

 a sector under the edge of the stage. 



Ij,^ Wi UUV, •JWl^V 



* Neues Jahrb. f. Mineralogie, Geologie, und Palaontologie, xxiii. (1906) pp. 

 163-86 (6 stereoscopic plates and 10 text figs. ; also as an extract frorn above 

 (E. Nagele, Stuttgart) ; and in an English trans. (E. Leitz, London), stereoscopic 

 plates not included. t 1907, p. 479. 



