]<)S NEW PAR ALLEL RUI E. 



Dcfci-iption of My infiiument for drawing parallel lines without fide devi- 

 Mr. Bofweil's ^[\qj^ jg formed of three rulers, laid parallel to each otlier, 



p.irallel rule to ' ' 



picverit lateral connected by two pair of moveable pieces, all of equal length, 

 Jevution, a;,(j parallel to each oilier; Uiefe pieces, where they meet on 



the middle rule, have their extremities formed into portions 

 of toothed wheeh, which Iqck into each other, as maybelecn 

 in the figure: the efFecl of thefe fegments of wiieels thus act- 

 ing in each other, is, thai all the lateral motion is transferred 

 to the middle rule, while the external rules move only in ao 

 oppnfiieand parallel diredion. 

 The contrivance This indrument will not be liable to the incorreflnefs ot 

 to prevent lateial^j^^Cg ^^^^^^ defcribed, for the following rcafons : 1ft. The 



dcvijcion cannot , , ■> t • i 



AiYtci Hti accu- tOothed fegments bemg in no way concerned in producing the 

 racy. Its fup- parallelifm of the infirument, its accuracy of parallelifm can- 

 niakes it fteady. "<^^ beat all affecled by any trifling incorreiftnefs of forma- 

 It is eafily made (ion in their parts. 2nd. All the co.nnccting pieces being 

 ^'^^ ' of equal length, can "be formed with more certain accuracy. 



3d. The conneding pieces palling from the fame extremities of 

 the external rules, give them a Heady fupport. For thefe 

 reafons, in my opinion, it potfelTes all the fieadinefs aind faci- 

 lity of formation of the common parallel rule, while it effec- 

 tually prevents the fide deviation, to which the latter is liable. 

 It mi"ht be It is not ablolutely necelFary to have more than one pair of 



made with but (he connetling pieces made with toothed fegments ; but as 

 toothed fe''- thefe fegments are eafily formed in the clock makers engine 

 ments, but two for cutting teeth in wheels, it can add little to ihe expence 

 Pole more un - ^^ ^'^^^ 'he two pair in this manner, as (bewu in the ligure, 

 form. and will make the inftrumcnt look more uniform. 



The middle rule ^he middle rule fliould alfo be made a little thinner than 

 ftmld be made the others, to prevent friction on the paper in its lateral move- 

 thinner than the . t • r 

 otherstoprcvent™'-''^*^''^^^"'" "l'^- 



triaion. In the defcriplion of this inftrumcnt, it will be obferved. 



Novelty of the j|^^j ,|^g novelty of it confifts in the application of the toothed 



jiiftrumcnt con- -' rr 



lifts in its tooth- fegments of the wheels to the ufe mentioned ; which I cannot 

 ed fegments. (inrl has ever been before ufed for this purpofe; and I think it 

 Reafons for flip- '''ghly probable it has not, as, befides its not being known to 

 pofing this in- gentlemen, whom I have confulted on this liead, moft likely 

 vcmion to be j^^ ^^ ac(|i]ainled wilh fuch matters, ihe fimplicity of the con- 

 trivance would probably have brought it into extenfive ufe, 

 if it had been ever known at any former period. 



I mention this only to fliew that,, before I claim the priority 

 of invention, I have taken forae pains to inveftigate my pre. 



tenfvons j 



