456 On the coniMrat'wc Strength of Chain Cables. 



the efficacy of the method. The truth of the latter, however, fol- 

 lows immediately from our theorem ; for since the attraction of 

 anv mass of iroii, whose parts are similar and equal on each side 

 the meridian, passing; through the compass, can be found in all 

 positions, the compass and mass retaining their relative situations, 

 from the attractions in any three ; it follows, that if we can find 

 a mass of iron whose effect shall double that of the ship in three 

 directions of the vessel's head; it will also, cceferis paribus, 

 double it for every other position of the vessel ; either with re- 

 gard to the points of the compass, or the situation on the globe. 



It was my intention to have added some further applications 

 of the method I have followed in this inquiry ; l)ut I have already 

 surpassed the bounds to which I had proposed to restrict my- 

 self : and I can therefore only arid my sincere wish that the 

 hitherto greatly neglected subject of magnetism may continre 

 to attract the attentioti which it has lately received Irom Govern- 

 ment; and by which alone we can hope to see explained maity 

 of those complicated pha?nomena of variation that, from the 

 widely extended observations they require, would perhaps for 

 ever baffle the most arduous exertions of individual talent. 

 Woolwich, June U), 1820. ' CMARJ.ES BONNYCASTLE. 



LXXI. Facts respecting the comparative Strength of Chain. 

 Cables on the Constinction of Capt. Samuel Brown, ani 

 the Patent Chain. Cable of'THOMAS Brunton, Esfj. ; and of 

 Iron Cables compared icith Hempen Cables: as elicited on the 

 Trial of the Causa Brunton against Hawks and others, be- 

 fore the Lord Chief Justice Abbott and a Special Junr, 

 2:1 1 h May 1820. 



A HIS was an action for infringing a patent granted to the plain- 

 tiif in the year 1813, for certain improvements in the construc- 

 tion, making, or manufacturingof ship*' anchors and windlasses, 

 and chain-cables, or moorings. The cause was of considerable 

 importance, and occupied the attention of the Court for upwarf's 

 of five hours. The case for the plaintiff was opened with gre;'t 

 ability by Mr. Scarlett, and was confined to an infringement of 

 one part on! V of tiie patent, namely, the chain-cables: but it vv^s 

 contended by the Solicitor- General for the defendants, that, as 

 the patent wa>< not for one, but three articles, if any one of them 

 were not new at the time of obtaining the p:itciit, or not useful, 

 the patent would be void. 



The Judge was not disposed to admit this: it v.-as possible thaf: 

 the oldness or inutility of any one of the three articles embrcaed 

 iu a grant, might render, the grant void as to that one, without 



destroying 



