230 WOODWARD, ON NOBERt's TEST-PLATE. 



than the rest of the fiekl, and a spurious line is seen in the 

 centre of the space between the adjacent lines. In the 

 second, third, and fourth bands, the spaces between the lines 

 are brighter than the rest of the field, and the first and last 

 lines of each band have a similar clear sjoace on their out- 

 side, beyond which, again, is a line-like shadow, which, in 

 the fourth and fifth bands, might be mistaken for additional 

 true lines. By changing the illumination, however, the true 

 character of these shadowy lines is plainly shown. Several 

 such spurious lines are to be seen beyond the first and last 

 true lines in some of the higher bands, but their true cha- 

 racter can also be determined by changing the^ illumination. 



In the first four bands the ruling is extremely regular, and 

 the lines in each successive band are not only closer but finer 

 than in the preceding ones. The same general characters 

 are presented in the higher bands ; but from the fifth band 

 on, the difficulties in the way of ruling such fine lines evenly 

 are not wholly overcome, and every here and there two lines 

 are ruled too close together, with a corresj^onding too great 

 distance on each side of the pair. 



The photographs of the eighth band, and of those subse- 

 quent to it, would seem to indicate that the progressively 

 greater fineness of the lines noticeable throughout is obtained 

 by diminishing the pressure on the point by which the 

 ruling is effected; moreover, the lines are not only at unequal 

 distances, but are somewhat wavy, as though, perhaps, the 

 point moved with a certain amount of tremor. These pecu- 

 liarities are best appreciated by examining the photo- 

 graphs ; but it must be confessed that the degree of regularity 

 and precision still exhibited in the fifteenth band is truly 

 astonishing. 



The negatives of the fifteenth band show the lines per- 

 fectly defined from one edge of the band to the other, but 

 they are so fine and close that they are indistinct in the paper 

 prints. A copy of this negative of twice the size has, there- 

 fore, been prepared, from which prints have been made, 

 which show the lines very well. A pale line at the right 

 edge of this band in the photograj)h may, perhaps, be a real 

 ruling, which would give 46 lines ; on the whole, however, 

 I am inclined to regard this line as a sj)urious one, and the 

 real number of lines as 45. 



Two photographs of the 16th, 17th, 18th, and 19th bands 

 have also been prepared, which show spurious lines in all 

 the bands, which in one of these photogi'aphs do not exceed 

 thirty in number ; in the other forty. In the photographs, 

 moreover, the spurious character of these lines is plainly re- 



