The Microscope. 



93 



microscope. A similar short tube of a size to receive the 

 ordinar}^ eye-piece extends from the other square face of the 

 prism. If now the microscope be placed with the tube horizontal 

 and the prism case with eye-piece be inserted, the ocular 

 pointed downward, an image of the object on the stage will be 

 projected on a piece of drawing paper beneath, provided of 

 course that there is sufficient illumination beyond the stage, 

 and that no light reaches the paper except that coming through 

 the objective. Personally I find this instrument much more con- 

 venient and satisfactory than the camera lucida. Mechanical 

 micrograms must yield, however, to photographs ; and the 

 micrographic science of the future will seek the aid of the 

 pencil less, and make more frequent use of the convenience and 

 accuracy of photography. Bausch & Lomb made and mounted 

 for me the prism described, and I have no doubt will be pleased 

 to duplicate it for others. 



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Editor The Microscope : — 



I have recentl}^ purchased of Messrs. Spencer & Smith, of 

 Buffalo, N. Y., their new series of first-class dr}^ objectives, con- 

 sisting of i of 150°, 1-5 of 150° and 4-10 of 130° ; their perform- 

 ance is so striking that a brief account of it may interest your 

 readers. 



In the first place they are practically perfect in respect to 

 color correction, their images in that respect being all that 

 could be wished, and quite as good as those of any apochro- 

 matic I have ever seen, and I have examined several of Zeiss' 

 best. In the second place the definition is perfect. The \ in 

 my hands performs especially well with oblique illumination. 

 The 4-10 is a most remarkable lens, performing equally well 

 with both axial and oblique illumination. The resolving power 



