NOTES. 99 



be reproduced by the half-tone process, and thus better results 

 obtained than are possible by either drawing or photography 

 alone — Modern Medici7ie. 



motee. 



DR. Cole, in his microscopical reminiscences, speaks most 

 highly of Spencer and Son's objectives. He says : — " I 

 know that with a Spencer one-tenth homogeneous immer- 

 sion, N.A. I "38, belonging to my frieid, Mr. Henry Benett, I have 

 resolved the dots in Amphipleiira pelliicida as clearly and distinctly 

 as those shown by Dr. Henry Van Heurck in The Microscope as 

 the result of photographing the frustule with Zeiss's two-millimetre 

 objective, N.A. r63. The result was achieved under the follow- 

 ing conditions, which, by measurement, increased the N.A. of the 

 objective from 1-38 to i'52. The objective was made with wide 

 collar correction for use with a lo-inch tube, the English and 

 American standard. By Dr. Henry G. Piffard's suggestion, the 

 tube was shortened to the Continental standard — six inches — the 

 systems closed, monobromide of naphthaline used as immersion 

 fluid for both objective and condenser, and a slide of Amphipleura 

 pellucida, which I had mounted especially in media of nearly 2*5 

 refractive index, placed in position on the stage. The result was 

 simply wonderful. The beads stood out as distinctly as those of 

 Pleurosigma angiilatum under a good immersion objective. The 

 same slide, under similar conditions, was afterwards shown by 

 Dr. Piffard to Spencer himself and Dr. Curtis, President of the 

 American Microscopical Society. Both were delighted, and said 

 they had never before seen such perfect resolution of the diatom. 

 I think Spencer's lenses, for all practical purposes, equal to Zeiss's, 

 while, having no fluorspar in their composition, they are not subject 

 to disease. No special slides, cover-glass, condenser, or eyepieces 

 are required." 



At the March meeting of the Royal Microscopical Society, 

 Mr. Conrad Beck told a funny story about a gentleman who had 

 invented a microscope which was said to possess the remarkable 

 power of showing chemical molecules. Mr. Beck went to see the 

 instrument, "and found that the microscope had not at present 

 done this, but it was about to do so. It was a home-made instru- 

 ment, and had been devised by a gentleman who had made the 



