The Microscope. 221 



The Doctor, being unable to see them, and my son having another 

 engagement, he took his departure. 



A number of gentlemen have each, with the same microscope, 

 objective, illuminator, and all accessories that we used when Dr. 

 Ward, and the other gentlemen, were present, resolved all bands up 

 to and including the 200,000, and others 150,000 and 160,000 lines 

 per inch — seeing plainly lines and spaces. Two of the gentlemen 

 have made reports regarding this, which may be found as follows: 

 Dr. T. F. C. Van.AIlen in The Microscopical Bulletin, and P. H. 

 Dudley, C. E., Vice-President N. Y. Microscopical Society, in the 

 journal of that Society, January, 1888. 



The successful resolution of the lines is not dependent on the 

 mode of ruling, but on the eyes. And, considering the admitted 

 inability in Dr. Ward's eyes, it would seem no more than an act of 

 justice to all concerned had the Dr. delegated his position on the 

 committee to some one whose eyes were more reliable, and who 

 would have been especially iinprejudiced as himself in making the 

 investigations. Good eye-sight is certainly an essential factor in 

 such close tests, as the resolution of even 120,000 lines per inch, and 

 there may perhaps be a reasonable doubt whether the Doctor was 

 able to resolve the 120,000 lines per inch, as he claimed he was able 

 to do. His admissions are, however, very candid, and his report can, 

 therefore, have no value as to the number or resolvability of the 

 rulings under discussion. 



Ruling on glass or metals is purely a mechanical process, and 

 as such the inventor of a special mode of procedure is fully enti- 

 tled to conceal his methods if he chooses to do so. I had thought it 

 best for a time, at least, to keep the manner in which I make my 

 fine rulings a secret. The reasons for doing so are too obvious, that 

 it seems hardly necessary to state them. But I can assure the Doc- 

 tor, and all others interested, that the process is purely mathemati- 

 cal, and there is no possible source of error to a careful manipu- 

 lator. 



Refen-ing to " the peculiarity of this illuminator, aside from 

 the oddity of its large size and square shape," I would say that it 

 is no larger nor more " odd " in shape than the nature of the con- 

 struction or mode of working requires it. A new working device 

 may have a new form without it being criticised and stamped as 

 " odd." Neither will it do for any man to consider himself the 

 author of the first commandment. 



