JOURNAL 



OF 



NATURAL PHILOSOPHY, CHEMISTRY, 



AND 



THE ARTS. 



yjNUJRr 1799. 



ARTICLE L 



Defcription of a new lt:Jlirument for drawing eqnldijlant and other parallel Lines ivith great 

 accuracy and expedition ; intended principally for the ufe of Engravers. With Specintcnt 

 of its Performance. By W. N. 



«3 O M E mouths ago I was informed by the Engraver who executes the plates for this 

 Journal, that an ingenious artift had conftruded a machine for ruling the fhades and 

 grounds of copper-plate engravings, which he not only ufed with great fuccefs in his 

 own bufinefs, but had fold to others under an engagement of fecrecy. How far this in- 

 formation might be ftri(£lly accurate, was of lefs confequence at the time this converfation 

 took place, than the confideration that it would be eafy to make fuch a tool, and render 

 Its advantages more general by publication. I then promifed to make one ; and having 

 now finilhed it, I take the earlieft opportunity of communicating it to the world. From 

 the preceding hiftorical ftatement, the reader will fee that I have no claim to the original 

 thought of fubftituting mechanical operation inftead of hand work in this department of 

 engraving ; and thofe who have feen the fcrew gear of Ramfden's great dividing en- 

 gine will alfo perceive, that 1 have done little more than diftribute the parts of this tool 

 ia what appeared to me to be the moft fimple and convenient manner. 



Fig. I. Plate XX. reprefents the inftrument of the fize of that which I have made. The 

 outline fe£lion, fig. 2, reprefents the fame viewed in a diredion parallel to the edge 0/ 

 the moveable ruler. The letters denote the fame things in both. A A A A is a frame 

 fixed to the drawing-board. It refembles that of a Aiding rule, and ferves to guide a 

 Hiding piece, which, lying in fig. i, immediately under the fcrew, could not with con- 

 venience be denoted by any letter. B C is a fcre^ of exadly forty threads in the inch, 

 but might conveniently be made of a coarfer thread. G H and E D are two cocks, the 

 former of which, GH, is fixed to the frame A, and bears a clip or pair of nuts, which 

 open and (hut with a joint like a pair of compafles, and either embrace the fcrew by a re« 



Vol. II.— Jan. 1799. 3 K gularly 



