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XXII. — On an Improvement in the Stage of the Microscope. 

 By M. S. Legg, Esq. 



(Read Jan. 26, 1848). 



It may be in the recollection of many members of the Society, 

 that last year our attention was directed to a useful mode of mani- 

 pulation, in a paper by John Anthony, Esq., " On certain appear- 

 ances observable in Navicula, from the Humber, by means of Oblique 

 Transmitted Light,"* by which certain markings existing in various 

 objects may be more readily observed: this communication has 

 doubtless had the effect of recalling the attention of microscop- 

 ists to a most eligible means of detecting lined structures. The im- 

 portance of employing oblique illumination, and the consequent 

 necessity of readily turning the object so as to place it at right angles 

 to its former position, and present it in an opposite direction to 

 the light, is sufficiently obvious, as, I trust, to justify the introduc- 

 tion of an improvement in the stage of the microscope by which 

 these desiderata may be accomplished. 



In the present arrangement of stages to microscopes as far as 

 I have as yet observed, the revolving-plate, when present, is placed 

 above the vertical and horizontal movements, the consequence is that 

 unless the stage-actions be brought to certain fixed points (in which 

 case the object must be adjusted to the field of the microscope by 

 the hand) the object is sure to be lost to the field of view directly 

 the revolving-plate is turned upon its axis, and if the adjustment be at 

 all out of place, the object will be found to describe an orbit round 

 the centre of the revolving-plate, which will increase in proportion to 

 the eccentricity of the adjustment. 



The above difficulties occurred to me, on a recent occasion in ex- 

 amining with a friend a specimen of Navicula, sent from America by 

 Professor Bailey, under a high power, and although the object, when 

 turned one quarter of a circle, was readjusted under a lower power, 

 it was with difficulty found again. 



* In Annual Report, 1847, p. 17. 



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