MEMORANDA. 



237 



moths, all of which may be beautifully seen under an ordinary 

 1-inch lens. With a ^-inch of moderate aperture (57°), and 

 Liebei'kuhn, the markings on several Diatomace^, as ]V. 

 formosa, elongata, Hippocamjms, Baltica, and Stmironeis 

 Phocnicenteron are splendidly shown in distinct ridfjes ; and 

 by using the draw-tube, a clear definition may be obtained 

 of P. anrjulat.um. I have, even with the same lens, exhibited 

 pal]>able indications of the lines (m an (American) Amician 

 test, P. gracilis. — 1\ G. Wright, M.D., Wakefield. 



Another Fiaidcr. — The best description of " Finder " for the 

 microscopist appears still to be an open question. 



It has been made abundantly evident that a strong pre- 

 dilection exists in favour of the ring, or circle around the 

 object, altliough the methods of effecting it have hitherto 

 been most uncertain in their results, as well as both difficult 

 to accomplish, and disfiguring in appearance to the slide 

 when required for the cabinet. To produce tliis ring by 

 " machinery " had occupied my attention long before Mr. 

 Tyrrell's description of a " Finder " appeared in your tiiird 

 number, but, on reading that, a new idea Avas suggested by 

 the rectangtdar scale. The result has been the cross lines 

 near the edge of the slide, as shown in t!ie accompanying 

 diagram ; but as it was soon made apparent that, in addition to 

 these, some definite indication of the precise spot was 

 absolutely necessary, the original idea was fallen back upon, 

 and has been put into practice with the most perfect success. 



Tlie annexed sketch is the full size of the original, attached 

 to a " quarter " of Ross. 



A, a brass cap, fitting upon the end 

 of the object-glass, which it entirely 

 covers up and protects from injury. 

 The upper end is tliin and slit so as to 

 move round easily without shaking. 



B, a stem soldered to the side of tlie 

 cap, with the upper end having two 

 projecting sides to steady the ends of 

 C, e, and^, which are firmly screwed to 

 it. 



C, an elastic arm of hammered brass, 

 which carries at its lower end, D, a 

 lever of thin brass plate, having a frag- 

 ment of diamond inserted in its thinner 

 end, and directly under the centre of 

 the cap A. 



c and f are two springs, pressing upon the shorter end of 



