Boijal Microscopical Sociehj. 95 



object is viewed as rows of ill-defined beads loaded witb colours, it 

 is difficult to avoid suspecting that the appearance is a spectral 

 illusion, resulting from some unexplained difiraction or interference ; 

 and this suspicion can hardly be dispelled from his mind by any- 

 thing short of rigid mathematical demonstration. In the 'Pro- 

 ceedings of the Royal Society' for June, 1873, an account is given 

 by Dr. Pigott of the appearances presented by a Podura scale 

 accidentally crushed by pressure, in which considerable tracts of the 

 markings appeared to have been resolved into an assemblage of 

 closely-packed spherules, and this appearance is assumed to confirm 

 the reality of the beaded appearance above mentioned. But con- 

 sidering the widely divergent views that have been entertained by 

 many competent observers as to the actual structure of the object 

 in question, the result of such severe mechanical treatment can 

 hardly be trusted as afibrding any satisfactory indication of struc- 

 ture ; and having seen the markings standing out like fingers from 

 the edge of an accidentally shced or folded scale, it is diSicult to 

 resist the impression that the latter, viewed simply as the result of 

 a mechanical injury, is much the more trustworthy. 



In the number of the Journal for ]\Iarch last, Dr. Pigott has 

 pointed out the source of some sj)urious appearances in the scales 

 of Lepisma SaccJiarina ; and the sentiment with which this paper 

 commences may be cordially endorsed, namely, that " until spurious 

 appearances are no longer accepted as true, it is impossible that 

 definition in the microscope can arrive at that degree of perfection 

 which is required by the spirit of the age." The author points out 

 that some of the spurious appearances produced in this object may 

 be obviated by cutting off, by means of a diaphragm with a small 

 aperture, the more oblique rays of the illuminating pencil : it 

 appears very probable that obhque illuminating rays are the fertile 

 source of many delusive appearances that are met with in micro- 

 scopic examination. 



Your President having fulfilled the office of Scientific Juror at the 

 Vienna Exhibition, it may be expected that some account should be 

 given of the microscopes and objectives there exhibited. There are 

 several reasons why a satisfactory account cannot conveniently be 

 rendered. In the first place, the extreme apathy shown by English 

 opticians with reference to the Exhibition led to the almost entiz'e 

 absence of English work, there having been in fact only one exhibitor 

 of microscopes. Mr. Pilhscher, and he, though established in London, 

 is by birth a Prussian ; and not even in his collection was there a 

 single objective of note, or of high power. It did appear, therefore, 

 that it would be hardly fair to compare objectives which were 

 exhibited with others which were not. Another reason is that the 

 time allotted to the jurors for the examination of objects and 

 apparatus was very short ; in fact, there was no time allowed for 



