Hie Advancing Powers of Microsoojnc Definition. 63 



correctiou, by simply reiideriug the illuminating pencil oblique, and 

 slightly withdrawing the objective from its first position, he obtained 

 a negative which displayed the bead-like or varicose appearance of 

 the ribbing more satisfactorily than he had j^i'eviously been able to 

 do.' A photograph of this appearance may be seen at the Eoyal 

 Microscopical Society's room." * 



The article in question next informs its readers that "Dr. 

 Maddox took up this much-controverted question, and after taking 

 great pains to remove oily matters by chemical solutions, he finally 

 made out a ribbed structure, to which lie thought the beaded aspects 

 were due-, as fine ribs crossing each other would give that efl'ect. It 

 does not seem, however, that the existence of such structures as 

 Dr. jMaddox figures negatives the existence of dej)03its in a more or 

 less beaded form ; nor do the investigations of Mr. Wenham, which 

 prove the reality of surface irregularities more or less corresponding 

 with the exclamation marks." f 



An interesting letter from The Chevalier Huyttens de 

 Cerbecq, in the January number, gives evidence of the extending 

 range of our Transactions. It begins with so piquant a sentence, 

 and appears to touch so closely the much-vexed question so long at 

 issue, that I may be permitted to make an observation or two upon 

 it. The Chevalier writes : — 



" I think it most important fur everyone that he should be able to see 

 through the microscope all that is to be seen, and nothing else .... 

 having studied for some months the scales of many butterflies and 

 moths of Em'oj)ean, Chinese, and Brazilian origin, I have been struck 

 by the elegance of the beaded ajipearauce those objects presented. I 

 may thus almost entirely confirm Mr. S. J. Mclntire's views : those 

 scales have almost all of them a beaded appearance, perfectl;/ defined : 

 but where I differ totally from this most distinguished Fellow of the 

 Royal Microscopical Society is, when he asserts in his paper read the 

 9th November, 1870, ' that those beads have no real existence as beads, 

 but are due to the interference of the rays of light by corrugated 

 membranes ; that they are, in fact, ghost-beads.' Reasoning upon this 

 hypothesis, it is not at all wonderful that Mr. Mclntire should have 

 attributed his failures, when ' he wished but could not call into 

 existence those almost palpable beads,' as he calls them himself, so 

 distinctly are they visible, ' to a predisposition of his mind, and to the 

 want of that necessary adroitness in manipulating which everyone 

 knows very well is not always at one's own command.' .... I think 

 it was due to an imperfect correction that Mr. Mclntire was not 



always able to see the beaded ajipearance of the scales In 



confirmation of the present letter, I beg the Royal Society to acce2)t a 

 dozen of my slides of butterfly scales, some of them selected." | 



* " Recent Microscopy," ' Pop. Sci. Rev.,' Jan., 1872. 

 t 'Pop. Sci. Rev.,' Jan., 1872, pages 11-H. 



X By the courtesy of Mr. Slack I have been (Jan. 11) favoured with a loan of 

 these interesting slides. The Rhdcnor {Surinam?) presents, '.'.hen " the colour tc-t " 



