( 116 ) 



\,—The " Colour Test " and Dr. Figoit. 



By F. H. Wenham, Vice-President K.M.S. 



In the last issue of this Journal we have another characteristic 

 Podura reiteration by Dr. Pigott. As I imagine that the number 

 of behevers in his ideas of structure is as small as the subject, I 

 have not been inclined to notice that already controverted, and the 

 patience of microscopists must eventually become exhausted by such 

 repetitions of the same theme. As he, however, appears to claim 

 without foundation some remarkable discoveries, I venture upon a 

 few reminders relating to this theory of beads and accompanying 

 colours. 



He says that having had the "boldness" in 1869 to state that 

 in the best glasses there is a certain residuary aberration, " this 

 raised a storm of opposition hardly yet subsided." This assertion 

 is not borne out by the facts, and is quite ridiculous. No such 

 storm was raised, to subside at last into a tranquil acquiescence of 

 any discovery whatever. 



It may be remembered that after several of these reappearances, 

 I, as nearly the only opponent, noticed his essays, and questioned 

 the inferences alone that were assumed, never doubting that 

 object-glasses were improvable, as my papers and work in this 

 direction testify. My argument was that Dr. Pigott had devised 

 no method of any utihty for deciding such errors, and that his 

 inferences were drawn from an erroneous interpretation of the 

 structure of known test-objects ; and when he further ventured to 

 publish some large diagrams, I asserted that these were evidence 

 that he was not even optically acquainted with the construction of 

 object-glasses that he would have us believe he was the means of 

 improving. 



As regards the now much-vaunted colour-test, I acquiesce in its 

 value, though it is no new feature ; for, in fact, this style of correc- 

 tion is coeval with the apjjlication of the single-front lens, intro- 

 duced by me more than twenty years ago, with the statement to 

 opticians that this appearance of ruby-tinged prominences on a pale- 

 blue or green ground was the criterion by which object-glasses 

 would be found to bear the highest eye-pieces, even with an elon- 

 gatrcd draw-tube. The glasses which demonstrated this are in my 

 possession still. This colour correction was not then hked. It was 

 I that Lad the battle to fight ! Nothing but the most colourless 

 appearances, as that given by the now nearly obsolete triple-front, 

 found favour. However, in justice to Mr. Andrew Ross, I may 

 state that he at once so far adopted my views, as to make a number 

 of |ths with a single-front lens, which, being very fine, had a good 

 run at the time, but as they were expensive to make, having three 



