82 COREESPONDENCE. 



lified assertion that it cannot be done, — though Mr. Wenham's memory 

 is too poor to recall what he had written, — and a peremptory challenge 

 to all mankind, " to get, through an immersion object-glass," any more 

 than he would get through any other. When Mr. ToUes wrote that it 

 could be done, and had been done repeatedly, Mr. Wenham says,* 

 " The ground is safe, and anyone that ignores or decries such a definite 

 principle must expect to forfeit all respect for his optical knowledge." 

 Perhaps Mr. Wenham has forgotten writing that also, 



Mr. Wenham, referring to the object-glass sent to him last year, 

 says that " The object-glass was not professedly an immersion one." 

 This is astonishing. I will say that it is professedly immersion, 

 and nothing else, will not perform at all well dry, and it is most 

 surprising that Mr. Wenham could have thought that a dry lens 

 should have been sent to him to illustrate a question that related 

 solely to immersion lenses. No wonder that he found his dry lens, 

 made twenty years ago, the better glass. 



That Mr. Wenham was not positively informed that the glass was 

 immersion only, is easily exjilained. It was expected that Professor 

 Markoe, who knew all about it, would deliver it personally to Dr. 

 Lawson or to Mr. Wenham, but, unfortunately, both those gentlemen 

 were absent at the time Professor M. was in London. 



Mr. Wenham writes of this glass, " I should have been quite con- 

 tent to try it if the adjusting collar had been pinned fast by the 

 Bender. . . ." This is quite a valuable suggestion for the future 

 when a glass is to be sent to a novice ; but, in sending to one of the 

 most renowned microscopists in Europe, it was not supposed needful 

 to give him instructions in manipulation, as to how to find the 

 maximum angles, as it would have been if sent to a tyro who had yet 

 to leai'n the A B C of his instrument ; and at that time there was no 

 knowledge or suspicion here that Mr. Wenham had other interest or 

 connection with any one firm of opticians than he had with any other. 



Finally, Mr. Wenham again says, " I am at length told that the 

 object-glass defines best with a cover yV*l^ thick." I must ask Mr. 

 Wenham to say who told him so ? Mr. W. has already been re- 

 quested to give his authority for his statement of Mr, Tolles' " admis- 

 sion " about this same lens, but he has forgotten to rej)ly. I hope 

 that he will not find it convenient to forget to answer my question. 



I will yield precedence to no one in my appreciation of Mr. Wen- 

 ham's services for many years past, by his beautiful inventions and 

 contrivances for improving the microscope ; all microscopists are 

 imder obligations to him for his valuable additions to their instru- 

 ments. Now they have greater cause than ever to thank him, for 

 his recent papers have drawn the attention of microscopists through- 

 out Europe and America to the work of a brother optician more 

 effectually than anything else could have done, and have exhibited 

 more conclusively the difficulties overcome, and illustrated more 

 strongly the skill manifested in so overcoming them, than anything 

 that the other would have ventured to say for himself. 



Charles Stoddee. 

 * 'Monthly Microscopical Journal,' vol. viii., p. 233. 



