On Mr. Bate's Improvement in Medal Ruling. 289 



b. The plate, covered with an etching-ground. 



c. The tracer ; and, 



d. The etching-point, at right angles to it- 



The arm c, d having a ruling motion horizontally across the 

 surfaces of a and b, and likewise moving freely in the direc- 

 tion c, d ; also, vertical motion being given to a, and hori- 

 zontal motion to b by the same screw; a series of lines traced 

 over the medal were described upon the plate in the follow- 

 ing manner: so long as the tracer moved over the plane sur- 

 face or ground of the medal, the point d described equidi- 

 stant lines upon the plate; but so soon as the tracer touched 

 a part of the raised surface or relief of the medal, it was raised 

 above its plane a quantity equal to the height of such relief, and 

 the line described by the etching-point was no longer equi- 

 distant, biit deviated an equal quantity upon the horizontal plate; 

 in the succeeding line, the tracer being raised off* still further 

 by the increasing height of the relief, the etching-point deviated 

 still further from the former line described upon the plate : the 

 continuation of this process produced a succession of deviating 

 lines upon the plate, which, opening as the tracer rose above 

 the plane of the medal and closing again as it approached that 

 plane, gave the effect of light and shade, in the printed im- 

 pression of the plate, so perfectly as, contrasted with the even 

 tint produced by the parallel lines representing the plane sur- 

 face of the medal, to convey to the mind almost a conviction 

 that the impression was raised above the level of the paper. 



However pleasing the effect of these impressions, they were 

 all distorted representations of the original (just so much as the 

 lines producing the representation deviated from the straight 

 line upon the medal); and having ascertained that this method 

 of producing such representations had been known to en- 

 gravers upwards of fourteen years, as likewise that an account 

 of it was given in a French work, called the "Manuel de Tour- 

 nure" it became evident that this distortion had suspended the 

 use of the process; the most valuable and interesting subjects, 

 those possessing the highest relief being the most distorted. 



It appeared to me, as it had no doubt appeared to others, 

 that this defect was irremediable, because the distortion arose 

 from the principle upon which the process was conducted; and 

 although the quantity of distortion might be diminished by 

 diminishing the motion of the etching-point, yet as this would 

 reduce the effect of the relief, it would impoverish the effect 

 of light and shade accordingly. 



My son, however, whilst engaged in the process of ruling 

 the large Napoleon medal, which required the application of 

 three whole days, observing that the thing to be desired was 



Third Series. Vol. 2. No. 10. April 1833. 2 P 



