NEW PARALLEL RULE. 



199 



tenfions; which I think is incumbent on every man to do on 

 fucb occafions: for, however fair the claim may be of inven- 

 tion, if a thing is well known to have been beiure done, it 

 ^tlead produces an aukward fenfation to the claimer; for 

 which reafon, thofe who accufe others of doing ihis, (liould 

 be the more cautious, that their accufation is fair in all its 

 parts; for oftentimes an external refemblance may fubfift be- 

 tween two contrivances, as between my inftrument and the 

 triple parallel ruler, and yet a fmail addition render their ef- a fmall addition 

 feds elTentially different; thus the triple parallel ruler admits Jo ^n inftrument 

 i of fide deviation, while my parallel ruler effeiStually pre- ^ers its effedls 

 i vents it. effenljally difFer- 



I My motive for publifliing the account of this inftrument is 

 j principally becaafe I think it a duty incumbent on every man, 

 ' who has contrived any thing that may be of ufe to the world, 

 ! to make it known as extenfilvely as poffible, which it certainly 

 will be by appearing in your Journal. 



Theinflrument from which tlie figure was drawn was made This inflrumeni 



according to my directions, by Mr. Banks, inftrument maker, ^^'^^ ^V ^^' 

 •».T • . o , , /- . r /• -.1 BiKks, 441, 



No. 4H m the Strand, and aniwers the purpoie perleciiy strand. 



well; of courfe any gentlemen who defire to ufe parallel 



rulers of this kind, may have them accurately made at the fame 



j place. 



I requeft the favour of your permitting the infertion, at the Typographical 



1 end of this communication, of the indication of feme (ypo- ^'"'O's '" Mi- 

 ... , . , . /^ Bofweil's lad 



I graphical errors, made in my paper relative to the perlonn- paper relative to 

 i ance at Tea of the fliip Economy, in your laft number; and the fliip Econo- 

 ] which I am the more anxious to have refiified, as fome of 

 I them entirely alter the fenfe of the paiTages where they occur. 

 1 Page 175, line 2, erafeit before could; line 6, transfer the 

 i bracket to het'oTezvhen in the next line; line 8, for is read are; 

 1 erafe the comma after is; and transfer the bracket to after 

 ^ proof ; line 9, 10, for dire6lioii read diredors ; page 176, line 

 i 15, i'oT/ource reaj^ purje; line 21, erafe nof before reji; page 

 1179, line 22, for point read front; line 37, for fmns lead 

 : frames; page l.SO, line 3, for fcurping read fcarfing. 



Some errors of the piefs are alfo apparent in the fide notes, 

 but I fliall not trouble you by pointing thera out, as they can 

 be rec^ififd by the meaning of the paifages to which they are 

 S added. I am. Dear Sir, 



Your very refpedlful humble fervant, 



J, W. EOSWELL. 

 Reference 



