34 



THE AMERICAN MONTHLY 



[February, 



never seen — or if he could photo- 

 graph the net-work so beautifully 

 shown in the drawing on p. 309. In- 

 deed, there is not much to be seen 

 with a microscope that cannot be 

 shown in a photographic print. 



This brings us to another point 

 which deserves consideration, because 

 it is quite likely to come up before 

 long in the discussion of fine rulings 

 on glass. It is now universally ac- 

 knowledged that the appearance of 

 an object under a microscope is no 

 positive indication of its structure. 

 The same is true of the photographic 

 representations of an object. As a 

 rule, what the eye sees the plate will 

 reproduce. Hence, to follow up the 

 example already suggested, if Dr. 

 Heitzmann should succeed in photo- 

 graphing the net-work, which is rep- 

 resented in his drawings as very min- 

 ute, this would only prove that he has 

 actually seen a net-work appearance, 

 which we are quite willing to admit — 

 but it would not demonstrate its ex- 

 istence in the structure. Nevertheless, 

 a photograph showing the net-work 

 would be of great value, since it would 

 indicate whether the object was in 

 true focus, and perhaps throw con- 

 siderable light upon the methods of 

 illumination required to demonstrate 

 its existence. Indeed, when such a 

 photograph is shown, the evidence con- 

 cerning the existence of the net-work 

 will rest upon a much stronger basis 

 than mere personal assertion, and will 

 receive more serious attention. 



As concerns the subject of fine rul- 

 ings, it has been proposed that pho- 

 tography be employed to test the ca- 

 pability of the microscope to resolve 

 closer lines than theory allows. But 

 photography alone cannot afford any 

 evidence whatever as to the number 

 of lines in a band. The most it can 

 do is to facilitate the counting of the 

 lines in an image, and thus enable the 

 observer to compare that number 

 with the number claimed to be ruled 

 by the maker. In this way it can be 

 made to do good service in refuting 

 the extravagant claims of those who 



believe they have resolved lines closer 

 than 150,000 to an inch. The sooner 

 the test is made the sooner will the 

 fact, already clearly set forth in these 

 columns, become patent, that the ap- 

 pearance, or the number, of lines in 

 an image is no proof of the lined 

 structure of an object, or of the close- 

 ness of its lines. 



Perhaps photography has found its 

 most extended use, in connection with 

 microscopical observations, among 

 those who are studying the schizo- 

 phytes of disease. Already it has 

 done excellent service in this field, 

 but while it shows the forms of the 

 minute rods and chains of spores suf- 

 ficiently well for the purposes of 

 specific identification, they are not so 

 sharply defined in the photograph as 

 when viewed directly in the micro- 

 scope. 



For a long time we have been ex- 

 pecting that some experiments would 

 be undertaken with a view to perfect 

 the processes of preparing and photo- 

 graphing such minute specimens. 

 There seems to be a good Held for 

 profitable experimenting offered here. 

 It seems not unlikely that the use of 

 an intense but diffused, and periiaps 

 also monochromatic, light for illumi- 

 nating the objects when photograph- 

 ing them, would greatly improve the 

 photographic prints. 



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