368 Miscellaneous Intelligence. 



advantage of employing iron drawn into wires, rather than forged into 

 bars, when the question relates lo its tenacity. 



The second object of the experiments was to ascertain the elonga- 

 tion of a wire when submitted to a weight, less than that sufficient to 

 break it. The elongation due to the mere rectification of the sinuo- 

 sities and curves in the wire itself, was found to be T *^ of the original 

 length, when a bundle of twelve wires of the second kind before re- 

 ferred to and 30 feet long, was charged with a weight of 6*621 lbs. 

 Another kind of elongation immediately precedes the rupture, and is 

 due to a slight diminution of diameter. It may be perceived when 

 the wire is charged with two-thirds of the weight, it is capable of sup- 

 porting ; and varies between 35 and 57 ten-thousandths of the length. 

 When the wire is annealed the elongation is very considerable, and 

 about thirteen- hundredths of the total length in all the wires tried. 



The influence of folds, returns, &c, on the tenacity of the wire was 

 of great importance considering the object of the experiments : the fol- 

 lowing are some of the practical results obtained. When a wire is passed 

 round a ring or cylinder, so as to return parallel to itself, and bear a 

 force applied to the two extremities nearly double that supported by the 

 single wire, it requires that the diameter of the cylinder round which 

 it passes should be at least Is inches. In proportion as the diameter 

 is smaller, or the curvature of the wire greater, its tenacity diminishes, 

 and the wire will constantly break at that place. One or more entire 

 revolutions of the wire on the same cylinder must be avoided, because 

 the friction resulting from such an arrangement, opposes the equality 

 of stress which is required upon each of the several wires constitut- 

 ing a bundle. 



After many experiments on the different means of joining wires 

 together, experience pointed out as the most efficient, one which 

 would perhaps not have been indicated by theory. The method was 

 to lay the ends side by side one over the other, and bind them round 

 for the space of at least 1} of an inch, by a smaller annealed iron 

 wire. Such a junction always resisted the proof's applied, the wires 

 constantly giving way at some other place. 



The preceding experiments were made with weights gradually ac- 

 cumulating, and unaccompanied by any sudden impulse or momen- 

 tum, but as in their application to the construction of bridges, effects of 

 the latter kind, would be continually occurring, further e>piiiments 

 were made of this nature. The wires were therefore charged with 

 about half the entiie weight they were able to support, and then other 

 weights dropped from different heights into the box containing the 

 previous charge. The latter force was always estimated by its mo- 

 mentum, and experiment proved that the second wire, for instance, 

 chargid with half the weight it was just able to bear, could sustain 

 without risk a quantity of momentum equivalent to 3000, the weight 

 being given in killograms (2. 207lbs.) and the velocity by the cente- 

 metres traversed in a second. 



