300 Remarks on Eigh-poioer Definition, [turnll jirffi"' 



Human red Uoocl-corpuscles. Magnified 1000 diameters, by 

 Powell and Lealand's immersion ^V- Negative 145 (new series). 



Section of an epithelial cancer of the larynx. Magnified 400 

 diameters, by Wales' ith. Negative 162 (new series). This 

 Negative is taken from preparation No. 2277, Microscopical 

 Section. The print shows the nuclei and cells of the growth with 

 great distinctness. 



Grammaiophora marina. Magnified 2500 diameters, by Powell 

 and Lealand's immersion -^^. Negative 151 (new series). 



Abmy Medical Museum, Microscopical Section, 

 January 4, 1870. 



The following note Dr. Woodward has requested us to append : — 



War Department, Surgeon-General's Office, 

 Washington, D.C, March 28, 1870. 



Note. — Since the foregoing essay was printed, I have obtained 

 a number of excellent pictures, with powers ranging from 400 to 

 1000 diameters, by using the ordinary oxy-calcium light as the 

 source of illumination. Some of these pictures were not inferior 

 to the best work I have done with the Magnesium lamp ; the process 

 employed was the same, and the times of exposure did not materially 

 differ. I will contribute fuU details in a short time. 



J. J. Woodward. 



V. — BemarJcs on High-power Definition. 



By F. H. Wenham, Vice-President, E.M.S. 



I AM induced to offer some observations under this head, in con- 

 sequence of the communications of Dr. Pigott. I had not the 

 pleasure of being present at the reading of the paper before the 

 Eoyal Microscopical Society, on 10th November, 1869, or I should 

 have made my comments at the time. Considering the large class 

 of observers that employ their microscopes chiefly for the 2)urpose 

 of resolving diflicult test-objects, and the form of their structure, it 

 is surprising that the alleged " bead structure " of the Podura and 

 other tests has excited so little discussion; and from the partial 

 acquiescence conceded by our respected President, I infer that this 

 structure finds credence amongst a number who interest themselves 

 in such investigations. Not having now the advantage of being 

 able to attend the meetings of the Society, I will take the question 



