274 CORRESPONDENCE. 



obsolete. At the time tlie belief was slow, tbougli in the few years 

 follo^\dng I had made a ith, two J, ths, two ^Vths, one ^ygth, and one 

 Joth, all on this system, and which were duly mentioned by the 

 President of the Microscoijical Society in his annual report at 

 the time. I was always glad to challenge comparisons, in order to 

 prove the superior advantage of this construction, yet it has only 

 recently been adopted by some of oui- most eminent English makers ; 

 and however this may now, in some slightly - modified form, be 

 announced as a " newly-discovered system," yet the principle remains 

 the same, and like in all exact sciences there is but one plan of 

 perfect construction. 



I have reason to believe that I am now unfolding a rigid law in 

 resi^ect to the relative foci and correction of the front and back 

 combinations, that applies equally to the }j inch and upwards in all 

 adjusting glasses. It has the merit of simplicity to recommend it, 

 and as soon as I can develop and define its conditions, I will give 

 the data from which I anticipate that mathematicians can work with 

 advantage to the science. 



Yours very truly, 



F. H. Wenham. 



Dr. Pigott and Mr. Hennah. 



2'o the Editor of the ' MontMy Microscopical Journal.^ 



ISIiLTON House, Claeence Stkeet, Brighton, Ajml 17, 1872. 



Dear Sir, — I cannot allow myself to be condemned by default, as 

 would be the case if Dr. Pigott's note, at page 173 of the last number 

 of the Journal, remains imcontradicted. 



Will you kindly afibrd me space in your next issue to state that 

 the photographs alluded to by Dr. Pigott are the same as those pre- 

 sented to the Society in March, 1871. They were the result of original 

 experiments, and so far were they from being taken from Dr. Pigott's 

 rods, or in any way in connection with him (as he ingeniously suggests 

 in the note), that I arranged the rods and took the photographs, and 

 then sent them to Mr. Curteis, who, for convenience of display at the 

 March meeting of the Society, further mounted them in a chromatrope 

 frame before he jjlaced them in Mr. Hogg's hand. 



I never heard of Dr. Pigott or anyone else having experimented 

 in the same way, until after my experiments had been published in 

 London ; and I can prove that Dr. Pigott, when he wrote his note, was 

 fully aware that the photographs were from rods mounted by me. 



I am. sorry so far to occupy your sjjace, but as the photographs 

 and rods were submitted to the Royal Microscoi)ical Society, as original 

 illustrations in proof of the difficulty of determining structure — as 

 well as a caution against too readily accepting Dr. Pigott's statements, 

 I must, in justice to the Society, as well as to my own position, 

 distinctly assert the originality of experiments undertaken to ascertain 



