124 Noherfs Nineteenth Band 



any part of it is actually resolved is settled beyond doubt, when that 

 part has been actually counted and the distances between the lines 

 have been measured. 



Truly yours, 



Charles Stoddeb. • F. A. P. Baknaed. 



It is now desirable to examine Dr. Woodward's pretensions a 

 little closer. It should be known if, or not, he always requires " the 

 lines to be correctly counted from one edge of the band to the other " 

 as proof that they are seen. Dr. W. often exhibits the resolution 

 of the 19th band to his visitors. Does he first always count the 

 lines ? Or does he not rather first resolve them, and then sometimes 

 count ? If he takes the last course, then he depends on his experi- 

 ence in determining that the true lines are visible, and his observa- 

 tions are as trustworthy as mine, no more so. Two gentlemen who 

 have witnessed the resolution both in Washington and Boston, 

 agreed in saying that that in Boston was the best. 



Has Dr. W. ever really " correctly counted the lines in any one 

 band?" which in his "judgment" is the sine qua non. 



After all that he has written it would not seem that this question 

 is yet to be answered, yet an analysis of his various reports and 

 letters shows that there may be grave doubts. 



In his letter of June 18th he says, " I supported my statement 

 by a count of the Lines, as well as by the photographs of Dr. Curtis." 

 " I thought, and still think, that Dr. Curtis's photographs were con- 

 clusive evidence that I had seen the true fines, although the spurious 

 lines shown on the edges of the band prevented them from serving 

 for the purpose of a count. I have recently made myself another 

 photograph of the same band, which will perhaps serve to convince 

 any who are still incredulous." 



In the ' Am. Jour. Sci.' for September, 1869, is Dr. W.'s original 

 account of his first resolution of the 19 th band. He writes, " I send 

 two prints on glass, of which the first shows the 16th, 17th, and 

 18th bands satisfactorily resolved. The second shows satisfactorily 

 the 19th band only. These pictures should be studied under a 

 power of from two to six diameters. In counting the lines on them 

 some doubt might arise, especially in the case of the 18th and 19th 

 bands, as to the real number of liaes; for certain spurious lines 

 which are interference phenomena may be seen on the margin of 

 the bands, and it is not always easy to tell which is the last real 

 and which the first spurious line. A comparison of several glass 

 positives from different negatives with each other, and with the 

 hands as seen in the microscope, lohere a change of focus materially 

 aids in the determiiuition, has led me to adopt the count above men- 

 tioned." Is this " correctly counting any one band from one edge 

 to the other," as in his judgment is absolutely necessary ? After aU 



