81 



Objective a* with variable initial magnification is the most suitable lens 

 for microscopic drawing, although other objectives of low and medium power 

 (to perhaps C incl.) may still be used with a fair degree of convenience. The 

 combination of a* with HUYGENIAN eye -pieces Nos. 1 5 results in almost 

 any desired magnification, ranging between 2,25 X an d 23 X being obtained, 

 while the diameter of the visual field varies between about 6 and 45 mm (Y 4 

 and ! 3 /4 in.)- Spectacle-lenses of from 1 to 5 dioptres yield magnifications from 

 1,25 to 2,25 diameters. A full description of this apparatus was published by 

 its designer, Mr. MAX BERGER, in the "Zeitschr. f. Instrkde.", vol. XXI, 1901, 

 pp. 171 175, to which we must refer those who wish to obtain fuller details 

 regarding its construction. 



The principal advantages possessed by this new apparatus, which we have now been 

 supplying for some considerable time, over other instruments constructed for similar purposes 

 consist in its being available as a drawing apparatus as well as a dissecting stand, that the 

 magnification is variable within a wide margin, and that even the largest objects can be 

 drawn in their entirety on exactly the same scale of magnification. The use of the 

 erecting microscope at the same time not only admits of a fairly large distance between 

 object and eye, but also permits the use of higher powers than objective a* for the 

 examination of particular portions of the object, without the necessity of removing the 

 latter, or parts of it, from the object-stage. 



For dissecting purposes the apparatus is furnished with a pair of hand-rests, 

 which will also be found most useful when drawing on a reduced scale. These 

 rests slip into slits at the two sides of the stage. 



Prices : Code-words : 



No. 102: Dissecting Stand P H ivithout optical equipment . . . Marks 260. . Patesea. 

 103 : with the drum contanining PORRO 

 prisms, No. 192; objective a*; HUYGENI AN eye-pieces 

 2 and 4/ lenses, 'Nos. 9 and 1O; 4 spectacle lenses ; 

 drawing prism, No. 1O9 ,, 410. . Paticojo. 



Stand P II is supplied in a spacious alder-wood cabinet. 



Stand P III. 

 Medium Dissecting Stand. 



As with Stand P I, a short column rises from the massive octagonal foot. 

 This column supports the stage (75 X 60 mm = 3 X 2 3 /s i* 1 -) with central 

 aperture. The rack and pinion movement of the objective-carrier slides inside 

 the column. Two leather -covered hand -rests may be attached to the stage. 

 See Fig. 40 on page 82. 



Illumination by transmitted light is effected by a large concave mirror 

 which is movable on two axes at right angles to each other. 



(Baal 



