ZOOLOGY AND BOTANY, MICKOSCOPY, ETC. 693 



according to the taste or temperament of the person guilty of the 

 misrepresentation), or to substantiate it by a complete demonstration. 



Mr. Nelson has attempted the latter alternative in a way which 

 we will not characterize, but which can be properly appreciated from 

 what follows. 



Mr. Nelson's original statement, it will be remembered, was that 

 the " Eoyal Microscopical Society " taught tbat " nothing can be 

 " Jcnoion about the structure of the diatomacese because all the diffrac- 

 " tion spectra are not admitted" a proposition which is so absurd on 

 the face of it, that we find it impossible to believe that Mr. Nelson 

 can have honestly supposed it to be held by any human being of only 

 average intelligence, much less taught by the " Eoyal Microscopical 

 Society." 



The proof of his assertion Mr. Nelson gives as follows : — 

 " Whether, for example, P. angulatum possesses two or three sets of 

 strias, whether striation exist at all, whether the visible delineation is 

 caused by isolated prominences, or depressions, &c, no Microscope how- 

 ever perfect, no amplification however magnified, can inform us. 

 Mon. Micr. Journ., xiv. 1875, p. 250." 



Thus, although the pages of this Journal teem with passages 

 which show that the views attributed to the Society are purely 

 imaginary, Mr. Nelson passes over every one of them, even the 

 authoritative paper of Prof. Abbe himself, and goes back more than 

 ten years to cite a paragraph from the Monthly Microscopical 

 Journal, which, as is well known, was an independent publication not 

 under the control of the Society. 



Is that a course of proceeding which entitles its author to demand 

 that he should be dealt with in a purely scientific spirit ? 



Moreover, the paragraph quoted, as will be seen, in no way sup- 

 ports Mr. Nelson's original statement, or shows that any one, much 

 less this Society, ever taught that unless all the diffraction spectra 

 are admitted nothing can be known of the structure of the diatom- 

 acea3. The Fellows of this Society hardly require to be reminded of 

 what the diffraction theory really does teach, viz. first, that according 

 to the coarseness or fineness of the structure, a greater or less number 

 of the spectra are admitted, and secondly, that the greater the number 

 admitted, the nearer will the image resemble the object. Were we 

 far wrong in saying that a writer had mastered but little of the 

 diffraction theory, who could sweep together the diatomaceae in 

 general — the coarse as well as the fine — as is done in Mr. Nelson's 

 original statement, and who was further so oblivious of what has been 

 said as to the indications of structure given by even a portion of a 

 set of spectra as to write that this Society taught that " nothing can 

 be known of the structure of the diatoinaceas, because " all the dif- 

 fraction spectra are not admitted " ? 



As we said before, it was so much of a puzzle to us to comprehend 

 why Mr. Nelson should go so far out of his way to try and fasten 

 upon people views which existed only in his own imagination that 

 we could only account for it by the supposition that he had been led 

 away by the practice well known in other quarters to which we 



