( 10 ) 



III. — Note on Br. Barnard's Remarks on " The Examination 

 of Noherfs Nineteenth Band." By J. J. Woodwabd, Assistant- 

 Surgeon, U. S. Army. 



My own paper " On the Use of the Nobert's Plate"* and Dr. 

 Barnard's reply,t state so fully the arguments in favour of a com- 

 plete count of the band on the one hand (my method), and on the 

 other, of a count of a measured portion of the band only, say 

 twenty to thirty lines (Dr. Barnard's method), that I think the 

 question may now advantageously be left by both of us in the hands 

 of those who are competent to judge of the comparative certainty 

 and accuracy of the two methods. 



Nevertheless I think justice to myself requires that I should call 

 attention to the contradictory interpretation which my distinguished 

 friend has been led to give to the same series of observations in 

 consequence of what I must regard as his misplaced confidence 

 in a method which I believe to be deficient in the accuracy required 

 for this purpose. 



Dr. Barnard's original observations were related by him in a 

 private- letter to Mr. Stodder, dated January 29, 1868, and Mr. 

 Stodder published them in a note to his paper " On Nobert's Test- 

 plate and Modern Microscopes" in the 'American Naturalist,' 

 vol. ii. p. 934 Mr. Stodder tells us that Dr. Barnard resolved the 

 nineteenth band with a Spencer's -j^th and a ToUes's ^th, both dry 

 lenses. With the former objective he made a series of counts of a 

 measured fraction of the band, which gave by reduction a series of 

 estimates of the number of lines to the English inch, 106,226 lines 

 being the smallest, and 115,474 hnes being the largest estimate. 



At the time Dr. Barnard made these observations the subject of 

 the spurious lines so readily developed on the plate had not received 

 due consideration. I had myself about the same time supposed that 

 I had resolved the nineteenth band with a dry Wales's |th, but 

 subsequently convinced myself that I had been deceived by the 

 spurious lines. 



The observations of Dr. Barnard recounted by Mr. Stodder as 

 well as some made by Mr. Stodder himself with a ToUes's immersion 

 ^th, reported in the same paper, became therefore the subject of a 

 private correspondence, and several conversations between Dr. 

 Barnard and myself, and that gentleman became so thoroughly 

 convinced that he also liad been misled by spurious lines, that in a 

 public lecture delivered before the American Institute in New York 

 city, November 25, 1868, he announced his conviction that the 



* This Journal, July, 1871, p. 26. 



t Ibid., October, 1871, p. 194. 



j Reprinted in the ' Quarterly Journal of Microscopical Science,' July, 1868. 



