1867.] 339 [Stodder. 



the lines tlo exist; and the resolution of them Avoiild evince the extraor- 

 dinary superiority of any objective, or of any system of illumination, 

 which should enable them to be distinguished." In the second edition, 

 1859, he substituted -g-j^oT ^^^' TaoFo ^""^^ adds: "There is good reason 

 to believe that the limit of perfection in the objective has now been 

 nearly reached, since every thing which seems theoretically possible 

 has been actually accomplished." In the third edition, (18(32) the 

 figures are again changed to g^Jrro- 



Messrs. Harrison and Solitt (Micr. Journ., Vol. ii, p. 01, 1864) 

 claimed that they had resolved the strife on AmpMpleura pellucida, 

 120,000 to 130,000 to the inch; and Mr. Solitt (Micr. Journ., viii, p. 51, 

 1857) expressed the opinion that lines 175,000 to an inch might with 

 proper means be seen. Here is a discrepancy important to be settled 

 if possible. In oi-der to do that, Messrs. SuUivant and Wormley 

 (Amer. Journ. Sc, Jan., 1861) made a careful examination of Robert's 

 plate of thirty bands, from yJy ^ to g-gL-g of a Paris line. They used a 

 Tolles's glp objective of 160° ang. aper., "an objective of rare excel- 

 lence in all respects," "besides -^^ and Jg of other eminent opticians, 

 both English and American." They were enabled to obtain an amplifi- 

 cation as high as 6000 diameters. "The true lines of the 30th band 

 p-plyg we are unable to see with any degree of certainty." They 

 conclude "that the lines on Nobert's test plate, closer together than 

 about the gy-Jo^ of an inch, cannot be separated by the modern 

 objective." This appears to have been the most thorough examina- 

 tion of the test-plate of which we have any account. Notwith- 

 standing that Sullivant and Wormley's paper was republished in 

 London, and that the London opticians have been making higher 

 power objectives since that time than they had ever made before, no 

 response has been made by Harrison and Solitt, or any others, to their 

 conclusion. The only Intbrmation we have as to what has been done 

 by European observers is a report (Quart. Journ. Micr. Soc, Jan., 

 1866) by Max Schultz of some trials on a test-plate. The highest set 

 which he has been able to define with central illumination is the 9tli 

 (== -56-^0-5- inch) which is resolved by Hartnach's immersion system 

 No. 10, and by Merz's immersion system -^j. With oblique illumin- 

 ation he has not been able with any combination to get beyond the 

 15th band (=9ooyo- inch). He considers the most diflicult specimens 

 of Pl<ntrosir/ma amjulatvm to be about equal to the 8th or 9th bands of 

 Nobert's lines, and the larger instances to correspond with the 7th. 



The present year, Dr. Woodwax-d, of Washington, D. C, resolved 

 the 29th and 30th bands, -go^, with Powell and Lealand's -Jg-, -j^j, 

 Hartnach's No. 10 immersion, and Wales's 1 with amplifier; Powell 

 and Lealand's J^ perhaps the best, but all very nearly alike (Quart. 

 Journ. ]Micr. Soc, Oct., 1867, p. 254). 



