W. &. Sullivant on Nobert’s Test-plate. 351 
amplification with illumination for counting them, and appara- 
tus for measuring the space in which they are counted, are all 
within the reach of the microscopist. 
Mr. Stodder’s views on the micrometry of the Nobert lines, 
are certainly untenable. He invests the subject with insurmount- 
able difficulties, and thus seems to ignore the only certain and 
reliable means of determining the nature, whether real or s 
, of any lines that may be seen on the high Nobert bands. 
_ His paper, nevertheless, will form an interesting part of the 
literature of a subject that has long attracted much attention, 
namely, the limit of the resolvability of lines under the micro- 
scope. The experiments recorded by Mr. Stodder go far toward 
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tion to that of sight; and that, especially when the eye is 
stained by an eager observer, and the imagination perhaps, 
plays under the pressure of a theory, it is quite possible, after 
a little, to see almost anything that is expected.” 
x Note—Since the above was in type the writer has been kindly presented by Dr. 
J. Woodward of the U. §. Medical department at Washington, with a series of 
area? Fees sual et ee + eR 
Into their true lines; the 15th band, however, (which is ruled to the sogon Of an 
ine ~ ~ requiring a hand-glass, magnifying four or five diameters, to show its 
istinctl 
© resolving and photographing such extraordinarily fine lines rank first among 
roa f eo of the nd on gure and attest the remarkable skill of Dr. 
‘© has accomplished both so successfully. +f att 
: The objective used was a z; inch made by Powell and Lealand; amplification 
AW) to 2,000 diameters. ‘The photographs of the 16th, 17th, 18th, and 19th bands 
Save, as Dr. Woodward remarks, only false or spectral lines. 
Lp Sia eda 
