321 



Mr. Ingpen said the fact was that all the genius of inventors 

 had been concentrated upon the idea of getting the best pos- 

 sible form of burner, so that it would be noticed that this part 

 of a 6d. lamp was practically as good as one which cost six 

 guineas, the idea being that of putting the greatest amount of 

 intellect into the cap, and then producing the whole thing at 

 the lowest possible cost. Some years ago he and Mr. Mogenie 

 had the matter under consideration, and they examined every 

 burner that was to be got. The workmanship of all was much 

 about the same, and they came to the conclusion that, with the 

 exception of the pinion, they could hardly hope to improve upon 

 the American model. 



The President having introduced to the meeting Herr Leitz, 

 of Wetzlar, to whom a hearty greeting was given, 



Herr Leitz said that in making experiments he had found 

 the apochromatic lenses, as usually made, were subject to some 

 disadvantages which seriously interfered with their usefulness. 

 The chief of these was that the glass was not sufficiently dur- 

 able, and therefore he had endeavoured, and succeeded at last, 

 in making a lens of hard glass in which the secondary spectrum 

 was absent in about the same degree as w^as the case with apo- 

 chromatics, and he was glad to be able to say that so far as 

 resolution was concerned, they could not see more difficult test 

 objects with the apochromatics than with his new series. He 

 had some specimens in the room of 2, 3, and 7 mm. focus, and 

 should be glad for any of the members present to test and com- 

 pare them with objectives of any other kind. 



The President said he had seen these glasses, and was of 

 opinion that they were certainly amongst the best which he 

 had examined. The No. 7 pantachromatic was almost exactly 

 equivalent to a quarter-inch, giving an initial magnifying 

 power of nearly 40. It was a most^ beautiful glass to work 

 with. 



Mr. Stokes inquired whether these objectives needed any 

 special form of eye-piece ? 



The President said that this w^as not necessary with the low 

 powers, but with the higher powers a compensating eye-piece 

 improved the image. 



Mr. T. F. Smith said he had found it of great advantage to 

 photograph an object without an eye-piece, and had got on very 



