NOTES AND MEMORANDA. 



A Finder for Hartnack's Microscopes. — In working with 

 one of Hartnack's microscopes, I found an inconvenience 

 which must have been felt by others, from the impossibility 

 of adapting any one of the ordinary finders to a stage so 

 simple in construction. Bridgman's finder, as described, 

 p. 43, of Beale's " How to work the microscope,^^ at first sug- 

 gested itself as available ; but this is clearly suited only to 

 microscopes having at least a sliding movement to the stage, 

 unless two are employed, one on each side of the stage. 



The following contrivance will, I think, meet every require- 

 ment. A line is ruled across the centre of the stage from 

 side to side, crossing this line at right angles are ruled two 

 lines about two inches apart, one on either side of the central 

 aperture of the stage. In order to use the finder, it will be 

 necessary to have a small white label affixed to each end 

 of the slide, the most convenient size being a round half 

 inch label. The portions of the lines on the stage left un- 

 covered by the slide being used for guidance, corresponding 

 lines are continued across the labels on the slide with a 

 pencil mark. Thus, at each end of the slide a cross-mark 

 will be formed, and whenever the cross-marks on the slide 

 are made to coincide with the crossing of the lines on the 

 stage, the part of the object required is in the field of the 

 microscope. 



This plan answers very well, but I was enabled to render 

 the effectiveness of the arrangement almost equal to the 

 graduated stages of the larger microscopes for accuracy in 

 finding, by the following very simple device. I roughened 

 each end of the slide by means of a corundum file and some 

 water, so that that the lines on the stage could still be seen 

 through the ground glass ends, and the points where they 

 cross marked on the slide with a pencil or ink spot. Many 

 points may thus be registered on the same slide. 



Not only are the ground glass slides useful for this pur- 

 pose, but I think they will serve a much more valuable pur- 



