AND MODERN MICROSCOPES. 135 



Tolles' i in 1863, and the next year Mr. Greenleaf saw the 

 same lines, unmistakably, with a Tolles' Vtt. Dr. J. J. Wood- 

 ward, of Washington, in a communication to the ' Quarterly 

 Journal of Microscopical Science,' London, October, 1867, 

 p. 253, states that with monochromatic light, and Powell 

 and Lealand's 3^'-^, ttV? and -^V objectives, a Hartnack immer- 

 sion. No. 11, and a Wales 4^, with amplifier, he satisfactorily 

 resolved the 29th and 30th bands of Nobert's test-plate. In 

 a letter to the writer written since, Dr. Woodward informs 

 me that the plate used was the same one used by Sullivant 

 and Wormly, as the 30th band was the finest on that ; the 

 result did not show that finer lines could not be seen. Dr. 

 Woodward informs me that, since writing that paper, he has 

 received a Nobert plate with the nineteen bands, and that 

 the covering glass was too thick for the -L objective, but 

 with all the others he was able to resolve the 17th band 

 (101,000 to the inch) ; the 18th and 19th he was unable to 

 resolve. Dr. WoodAvard has sent to me a j)hotograph of the 

 16th, 17th, 18th, and 19th bands, taken by Dr. Curtis with 

 the Powell and Lealand ^V- In the photograph the lines 

 of the 16th and 17th bands may be counted with some 

 difficulty, but if the whole band is copied, or if the bands 

 are of the width of ^roVo of an inch, there are not lines 

 enough. The lines of the 18th and 19th bands cannot be 

 counted in the photograph. From this it will be noticed 

 that Dr. Woodward has resolved finer lines than any other 

 observer had yet seen, so far as report gives us any informa- 

 tion. 



My esteemed correspondent, M.* Th. Eulenstien, of Stut- 

 gard, Wirtemberg, Avrites to me, under date of Dec. 17th, 

 1867, " I have myself resolved the 14th band with a -^ Powell 

 and Lealand, and also, but less unmistakably, with No. 11 

 Hartnack's immersion, with oblique light." " Nobert him- 

 self has never seen with his highest powers higher than the 

 14th." " This will show you the Continental state of affairs.^' 

 Mr. R. C. Greenleaf and myself have lately tried several 

 objectives, and the result is a^^pended below.* 



* Wales' \ ang. ap., 140°, B eye-piece, power 475 diam., 



sunlight oblique ..... 8tli band. 



Hartnack's immersion No. 10 z= J-, ang. ap. 155°, power 



1062, B eye-piece, light oblique . . . lOlh „ 



Nachet's immersion No. 6 = -^-^, B eyepiece, sunlight 



oblique ....... 8th „ 



Nachet's immersion No. 10 = ^V ^ eye-piece, sunlight 



central ....... 9th „ 



Nachet's immersion No. 10 =: -g^y, B eye-piece, sunlight 



oblique ....... 12th „ 



