276 COERESPONDENCE. 



Dr. Pigott's unsupported assertions, that tlie Poclura note mark- 

 ings, called by him " shillelahs," and recently " tadpoles," are oj)tical 

 illusions, have been thrust before us ad nauseam for years past. If I 

 have disputed this in strong terms, and as I have already controverted 

 this repeatedly, it may perhaps be unnecessary to go over the same 

 ground. 



I repeat the sentence quoted in italics by " Fair Play." " I know 

 not one microscopist of any note who has investigated the subject that 

 believes in him " (Dr. Pigott), and will discuss the subject with any 

 observer of note holding his oj)inion, and giving a bond fide name, 

 with freedom from that acrimony which " Fair Play " so readily 

 attributes to another from his own example. 



As " Fair Play" supposes that Dr. Pigott's views are to be finally 

 established, and says " his recent researches in circular solar spectra 

 and test definition opens the whole question anew, to those who are 

 willing to search rather than carp and cavil at what they will not or 

 have not themselves investigated " (the italics are mine), he compels me 

 to notice that which I should not otherwise have thought worth while. 



At page 18 of the 'Monthly Microscoj)ical Journal' for July, 

 1873, Dr. Pigott announces, in huge capitals (as I find it) his 

 forthcoming CIRCULAE SOLAR SPECTRUM; I consequently 

 anticipated some new fact, or that something original had been ob- 

 served in the properties of light. Much to my surprise, however, 

 under this imposing title, did I find merely the colour rings, caustic 

 curves, &c., derived from a highly luminous point, such as that from 

 a sunlit mercury globule, perfectly well known a quarter of a century 

 ago to those engaged in the correction of object-glasses, and employed 

 to discover errors of centering, figure, or oblique pencils, adjustment, 

 distance of lenses, &c., having the engine-turned patterns, blurred 

 disks, and curious chequered forms, some of them in regularity, with 

 almost diatom-like markings, associated with bright colouring. These 

 familiar aj>pearances, which anyone can produce, indeed " opens the 

 question anew " — to himself at least — and with a very proper begin- 

 ning, I readily admit. 



As there is nothing in his letter that requires scientific considera- 

 tion, I now take leave of '' Fair Play " and his " few temperate re- 

 marks," asking your readers to consider how far the inconsistent title 

 he has assumed has exalted the cause that he advocates. I have felt 

 as if replying to a nonentity, where a name might perhaps be 

 entitled to some respect. 



F. H. Wenham. 



P.S. — As I have already stated, I repudiate making any " insinua- 

 tions against Dr. Pigott's character ; " but I take this oi>portuuity of 

 exj)laining, as certain remarks appear in a letter of mine (published 

 at page 17, No. 443 of the ' English Mechanic ' for September last), 

 written in the belief that the publication of certain correspondence 

 had been at his request (as stated therein), and which I considered_not 

 to his credit. Seeing he has come forward candidly to disclaim all 

 responsibility for the appearance of these letters (see last Journal), I 



