G94 SUMMARY OF CURRENT RESEARCHES RELATING TO 



referred, and had attributed to tlio Society the most absurd views for 

 tbo purpose of glorifying himself by showing how he could dispose 

 of them. 



Wo fail to see the good of such tactics, for even if for the timo 

 the writer is able to pose as a victor, the victory in a few weeks is 

 turned into worse than a defeat when the demonstration of the dis- 

 creditable arts to which he has had to resort is published. 



Mr. Nelson deprecates the sledge-hammer being applied to bim. 

 We shall bo only too glad to put the sledge-hammer back in its place 

 when ho returns to the usages not only of scientific but of all decent 

 persons, and abstains from the misrepresentations in which he bas 

 recently indulged. 



Interpretation of the Six Spectra of Pleurosigma angulatum. 

 This article by Mr. E. M. Nelson * is the most striking instance 

 which we can recall, at any rate in microscopical matters, of a critic 

 being " hoist by his own petard." 



The article purports to show the error of the view of Dr. Eichhorn 

 in his paper on this subject, referred to in this Journal, I. (1878) p. 186, 

 and while to some extent excusing Dr. Eichhorn for his mistake, 

 insists that the support given to him by " the E.M.S. is quite un- 

 pardonable." 



Now, the simple fact is that Mr. Nelson has found a most egre- 

 gious mare's-nest. The very thing that Mr. Nelson declares Dr. 

 Eichhorn ought to have said, but did not say, he does say. The 

 very thing that Mr. Nelson considers Dr. Eichhorn to be wrong in 

 saying, he does not say. 



Mr. Nelson has mixed up the images seen in the Microscope and 

 the real structure of the objects which furnish those images, so that 

 while Dr. Eichhorn who had. " never seen a diatom " (as Mr. Nelson 

 himself says) deals necessarily exclusively with images, and those 

 false ones, he is denounced for his fallacies in dealing with true struc- 

 tures ; and this Society, who for many years have published in every 

 number of the Journal a table showing how many lines to the inch 

 can be resolved with a given aperture, are supposed to believe than an 

 aperture of 0-50 N.A. will resolve 100,000 per inch ! | 



All this arises from the fact that Mr. Nelson has never read 

 the paper which he elaborately criticizes, either in the original 

 German or translation. This is a strong assertion to make, and we 

 should not venture to do so at second-hand, or if we had not extracted 

 the admission from Mr. Nelson himself. 



* Engl. Mech., xliii. (1886) pp. 337-8 (5 figs.) and 396. 



t It would hardly be fair to deal seriatim with the various mistakes of Mr. 

 Nelson's paper as they all flow from the one cardinal error of supposing that 

 Dr. Eichhorn had predicted " true markings " in place of admittedly false 

 images, but there is one matter of fact which should be corrected. Mr. Nelson 

 declares that the points in question cannot be seen in the way described, but only 

 by enlarging the diameter of the dioptric beam and cutting out the six spectra, 

 " and until they are cut out nothing will be seen of the intercostal markings." 

 The simple fact is that they were seen by Prof. Abbe, Mr. Stephenson, and other 

 Fellows with a very narrow dioptric beam and without one of the six spectra 

 being cut out. 



