818 



SUIIMAEY OF CURRENT RESEARCHES RELATING TO 



ing instances of this will bo found in tlic author's statement (p, 268) that a 

 passage quoted from Prof. Abbe " clearly moans that, given perfect 

 " correction of the objective, there is perfect definition of the object, which 

 " to me seems to contradict the former ^mrt of the pajicr." The writer there- 

 fore has avowedly not a glimmering of a notion of that most elementary 

 point of the diffraction theory — the difference between^ " delineation " 

 and " definition," or that perfect definition is quite consistent with 

 imperfect delineation. 



If the only result of publishing the paper were to raise a laugh at 

 the expense of the author, the matter might be treated as not being of 

 more than personal interest, but when we find the Quekett Club printing 

 such rubbish, it is necessary to make a protest in the interest of micro- 

 scopical science against so retrograde a proceeding, and this the more so 

 as it was at the Quekett Club that one of the earliest demonstrations was 

 given of the fact that microscopic images cannot be interpreted by 

 simply " believing the evidence of one's own eyes," as it is now suggested 

 is all that is necessary. 



In another part of the same No. Tive have a bewildering mixture of 

 conflicting statements.* As will be seen from the extracts we print 

 below, the speaker declares as " absurd on the face of it, and Prof. Abbo 

 did not believe anything of the kind," just what Prof. Abbe, as appears 

 from another part of the same Journal, does believe, and which is nothing 

 less than the cardinal fact of the diflfraction theory, while the speaker 

 himself later on, apjiarently quite unconscious of the discrepancy, states 

 his belief in the very thing which ho had before denounced as absurd. 



Speaker's first Statement. 

 "There had no doubt 

 "been gome very objec- 

 "tionuble passages written 

 "in conneotion with the 

 "subject — not perhaps by 

 " Prof. Abbe, but in such 

 " a way aa to appear to 

 "put them into Prof. 

 "Abbe's nioulh ; such for 

 "instance, as the state- 

 " ment that because the 

 " whole of the diffraction 

 "imap;es were not taken 

 " in, therefore tbe whole 

 "structure of the object 

 "could not bo known. 

 "That, of course, was 

 " absurd on the face of it, 

 "and Prof. Abbe did not 

 " believe anything of the 

 "kind." 



The mischief of all this is that it must necessarily have the effect of 

 making a student believe that the subject is so confused and unsettled 

 that it is of no use to try and understand it. 



There is plenty of room for most interesting criticism on the subject 

 of diffraction, but to be worth printing it must be founded on intelligent 

 doubt, and must not consist of raw and undigested ideas arising from 

 simple ignorance of the subject, which renders it necessary to win over 



• Joum. Quek. Micr. Club, iii. (1888) p. 288. 



Prof. Ahhe's otcn Statement. 

 " Perfect similarity bc- 

 " tween the microscopical 

 "image and the object 

 "always depends on tlie 

 " admission to and utiliza- 

 " tion by the objective of 

 " the whole of the dif- 

 " fracted rays whicli the 

 " structure is competent to 

 "emit. When a jiortion 

 "only of the total diffrac- 

 " tion fan appertaining to 

 " a given structure is lost, 

 " the image is more or less 

 " incomplete or dissimilar." 



Sjjeakcr's second Statement. 

 " With tlieso difficult 

 " objects, however, though 

 " they could gut a fair 

 "knowledge of them witli- 

 "in the limits of their 

 "optical power, yet they 

 " came at length to a point 

 " wliere the largeness of 

 " the angle required wa8 

 " such that they could not 

 " yet grasp tlie diftVaction 

 " spectra, and at that point 

 " their entire knowledge 

 " necessarily ended," 



