308 On a New Critical Standard Measure ['JS,'.'r'J?iI.!?^™t'fj7a' 



to Lave seeu tliem by sunlight recently, wliich claim needs some 

 confirmation, as liis No. 10 failed so completely in my bands." 



" Since the foregoing was written, Dr. Barnard has made more 

 trials, aDd I am well satisfied bo has seen the 19th band with a 

 Spencer yVth and Tolles' ith, both dry objectives." 



" Dr. i3arnard counted the lines five times, giving a mean of 

 110,820 lines to the inch, instead of Nobert's number, 112,688." _ 



It should now be stated that "Colonel Woodward* declares his 

 behef that Mr. Stodder saw but could not count the lines. At this 

 date spurious lines were so numerous that photographs could not be 

 relied upon for counting them." He concludes his paper with in- 

 dicating an ingenious mode of counting the fines with a black spot 

 projected upon a plate of glass, upon which the image of the lines 

 is focussed direct from the microscope, without the intervention of 

 an eye-piece. And in a note he says, " Dr. Barnard informs me 

 (notwithstanding the former results), July 21, 1868, that his 

 opinions are not matured, and that he intends to make further 

 ofjservations." 



Mr. Mayall, junr.,t writes — "Dr. Woodward seems not to have 



been sure of the accuracy of the count of his photograph 



He says it shows the 12 th band resolved into 37 lines, and further 

 on he says fortj/ is the real number in the band." 



" It was only after frequent trials that I could be assured of 

 distinguishing readily between the appearance of the two consecu- 

 tive lines, and those woolly or wavy-looking lines which are shown 

 either by defective illumination or by want of power in the objective, 

 but which are sometimes believed to be imperfectly-ruled lines." 



" With the Ith and iVth of Pioss, and the aVth by Smith, in the 

 possession of this Society, and with a ith, iVth, iVth, and ^Vth by 

 Powell and Lealand, all dry objectives, on a new 19-band plate, 

 all the bands beyond the i^th seemed imperfect — the lines were not 

 8q)arated." 



Subsequently, Dec. 1868, Colonel Woodward's paper, * Further 

 Remarks on the New Nineteen-band Plate of Nobert and Immersion 

 Lenses,' gives us precise details of the resolution, accompanied by a 

 beautiful photograph of the resolved fines, and informs us with a 

 magnanimity which does honour to America: — 



" For other lenses carefully tried on the same plate, the J th 

 Wales, aVth and sVth Powell and Lealand, aU dry lenses, resolved 



the 15th band but not the 16th The utmost that a Tolles' 



immersion ith, only a strong ith English standard, was to show the 

 true lines of the 14th band. 



" A Tolles' immersion yVth, of 175° of aperture, was received at 



* ' Quarterly Journal of Microscopical Science,' Oct., 18G8. 

 t 'Monthly Microscopical Journal,' Feb , 1869. 



