Royal Institution of Great Britain, 4^3 



The maximum quantity of such "wire drawn through a metal -plate 

 has not been two miles in leni^th, and there it has been found neces- 

 sary to break the wire and begin with a new hole, as the old one was 

 worn too large, and the increased diameter of the wire occasioned 

 a c^reat loss of valuable material. Holes have been pierced as fine 

 as the T5"»wth of an inch in ruby and sapphire, and the gilt wire so 

 obtained, and afterwards flattened, has so attenuated the gold, thj^t 

 its calculable thickness was less than the Tscs^s^c^th of an inch ; 

 a platina wire being placed in a silver wire of 90 times it3 diameter, 

 and the latter reduced to uVsth of an inch, the former was reduced 

 to the undetectable thickness of icscssth of an inch. Mr. B. stated, 

 that he had employed various stones and gems with as various 

 success — agate, jade, heliotrope, chrysoberyl, ruby, sapphire, and 

 diamond. The chrysoberyl, ruby, and sapphire were the best : the 

 first, for its toughness and hardness ; the latter, for hardness princi- 

 pally. The diamond failed from the difficulty of polishing the hole*. 



The invention was unsuccessful for iron-wire, because the mate- 

 rial was found to be too intractable, and stones of sufficient mag- 

 nitude could not be procured at a moderate price; but if this 

 could have been effected, the value of the invention, as applied to 

 the manufacture of wire for carding-machines, would have been 

 very great; because wire perfectly cylindrical and equal is a 

 desideratum. It would, also, have been of great value for nuisical 

 wire; — not that pianoforte-makers and tuners would have been 

 sensible of its excellence, as their present test of the fitness of 

 the wire which they use is the twisting which it will bear — ^ 

 quality found in high perfection in tin wire, and least of all in 

 steel. 



Mr. B. adverted to the vague and confused tables of ductility 

 and tenacity usually found in works upon the qualities of metals. 

 Ductility is a term usually employed to express the quality of the 

 metal upon which forces act to reduce it to wire ; but if this mean 

 in the way wire is usually made — that is, drawn through a hole- 

 it includes two qualities : the tenacity of the wire drawn, which 

 must exceed the resistance in the whole of that portion which is to 

 be drawn ; aud the hardness or softness of the metal which is sub- 

 jected to tlie reduction. Thus, the ductility of steel and of tin 

 would approximate closely; for the softness of tin is considerable, 

 but its tenacity very little; whilst the hardness and intraqtibility of 

 steel is so great, that it exceeds its high quality of tenacity, and 

 renders the difficulty nearly equal of drawing steel and tin. But 



♦ The mode of making these holes was also stated by Mr. B., and will be 

 made the subject of a future notice in this work. 



