132 SUMMARY OF CUERENT RESEARCHES RELATING TO 



After this digression, I return to the consideration of the credi- 

 bility of Mr. Fasoldt's claim that he has succeeded in ruling lines 

 1,000,000 to the inch. At this point it is only fair to say that until 

 recently I have shared in the general incredulity with which Mr. 

 Fasoldt's claim has been regarded. Indeed, I still think he has placed 

 the limit just a trijBie too high. But if the limit is reduced one-half, 

 I am by no means sure but that it may be reached. Possibly it may 

 have been already reached. But what evidence have we that it is 

 possible to see single lines of this degree of fineness, granting that 

 it is possible to produce them ? The answer to this question involves 

 another inquiry, viz. has the Microscope reached its highest visual 

 possibilities ? Here again it is necessary to draw a sharp distinction 

 between visibility and resolution. In the matter of limit of resolu- 

 tion it must be admitted that little or no progress has been made 

 since the resolution of Nobert's nineteenth band. The distinguish- 

 ing feature of Nobert's lines is a certain boldness which enables them 

 to be photographed, and it is to photography, supplemented by the 

 statement of the maker, that we owe the certainty of the resolution of 

 the nineteenth band. But all attempts to go beyond this band, even 

 with Nobert's later plates, have proved failures. I cannot learn that 

 any one has yet succeeded in photographing a Fasoldt plate as high as 

 100,000 to the inch. Certainly various attempts which have been 

 made with bands of my own ruling higher than about 70,000 have 

 not been successful. There are several Nobert plates of the new 

 pattern in this country. They run as high as 240,000 lines to the 

 inch,* but who has gone beyond the number of lines in the nineteenth 

 band ? f With great respect for the honest belief of several micro- 

 scopists who claim to have resolved Fasoldt's bands as high as 

 152,000 to the inch, I must yet hold to the opinion that in no case 

 has the resolution been proved by a test which will be generally 

 accepted by microscopists. There is one test, and only one, which is 

 absolutely decisive — viz. the one originally proposed by Nobert, that 

 of ruling a definite number of lines in a band of given fineness, and 

 keeping the number secret until the microscopist could give the 

 correct count, not merely in one instance but in several. Even here 

 we must depend upon the honesty of the maker in revealing the 

 correct count. Has the correct count been made in any Fasoldt plate 

 as high as 100,000 to the inch ? I think not. Has it been done 

 with any band of my own ruling of the same degree of fineness? No. 

 Let us marshal the evidence pro and con, offered by experience. 



(a) Mr. Fasoldt's finest bands present a perfectly smooth and 

 uniform surface. They have well-defined limits, and the width of 

 the bands is what it should be by the number of lines claimed to be 

 ruled. 



(6) According to present experience single lines can be ruled 



* The highest is 1/20,000 of a Paris line, i. e. 224,000 to the English inch.— 

 Ed. J.K.M.S. 



t Mr. E. M. Nelson claims to have resolved the next finest band to the 19th, 

 viz. the 11th band of the latest 20 band plate, the lines of which are at the 

 rate of about 123,000 to the inch.— Ed. J.R.MS. 



