96 



who stated iu his accompanying letter that it might be regarded 

 as a fair sample of Mr. Tolles' work. With this leus, after 

 uutnerous careful trials, I was unable to see the true lines beyond 

 the sixteenth band. 



It will be seen, then, that in my hands the best definition was 

 obtained by the immersion ^ j^h of Messrs. Powell and Lealand ; 

 and I may here say that, on a thorough comparison of this ob- 

 jective with the dry -^jth and ^^'^th of the same makers, 1 found 

 that not merely did their new lens resolve higher bands on the 

 Nobert's plate than could be made out with the oVth and 3^^^' 

 but that it would bear the use of eye-pieces and amplifiers so as 

 to give higher powers than can be obtained with the 5^^^^' ^^"ith 

 much better illumination, with better definition, as well as 

 with a practical working distance. The lens may therefore be 

 especially commended for anatomical work when the highest 

 powers are desirable. 



In conclusion the author referred to some remarks by Mr. 

 Mayall, Junr., in a paper on " Immersion Objectives and Test 

 Objects." 1 



Mr. Mayall says : — " Dr. "Woodward seems not to have been 

 sure of the accuracy of the count he made on his photograph : 

 for although iu one part of this paper in the current (October) 

 number of the Journal of this Society, he says the photograph 

 shows the twelfth band as resolved into thirty-seven lines, farther 

 on he says that forty is the real number in that hand." This 

 misapprehension on the part of Mr. Mayall arose from a mis- 

 print in the Journal. On p. 231, fourteenth line, " 12th band " 

 reads in my original MS. "13th band;" on the thirtieth line of 

 the same page, I find " 12th band " printed instead of " 19th 

 band," which is the reading of the original.- The same article 

 contains some other singular misprints, most conspicuous among 

 which may be mentioned, " Startiug's work on the microscope," 

 p. 225, instead of Hartings ; and " Grreenhap," p. 288, instead of 

 Greenleaf. At the time my article was prepared I had no doubt 

 whatever of the true number of lines iu all the bands resolved, 

 except the fifteenth, about which, as I stated, I was uncertain 

 whether the true number of lines was forty-five or forty-six. At 

 present, additional work has satisfied me that forty-five is the 

 number, and I am also well assured of the correct number as 

 given above for the remaining bands. I freely admit that the 

 diflBculty of determining which is the last real, and which the 

 first spectral line is very great even on glass positives ; neverthe- 

 less, a comparison of several photographs with each other, and 

 with the bauds as seen in the microscopes, has satisfied me that 

 my count is correct. 



1 See this Journal, July, 1869. 



' Dr. Woodward was, unforlunatcl.y, not able to correct his own proofs, on 

 arcouiit of distance. The errors pointed out read in his original MS. as 

 they were printed. We are glad to have the opportunit;y of correcting 

 them. 



