346 
METHOD OP DRAWING FINE WIRES. 
Experiments 
chiefly relat- 
ing to the tena- 
city and ina- 
naeementof 
such wires. 
Management. 
\ 
The extremity of a platina wire having been fused* into a 
globule nearly one-fourth of an inch in diameter, was next ham- 
mered out into a square rod, and then drawn again into a wire 
.^ 3 - of an inch in diameter. One inch of this wire duly coated 
with silver, was drawn till its length was extended to 182 
inches, consequently the proportional diminution of the dia- 
meter of the platina will be expressed by the square root of 182, , 
so that its measure had become--^-— = ~ . The specific 
gravity of the coated wire was assumed to be 10,5, and since 
the weight of 100 inches was 114 grains, its diameter was 
inferred to be - 5 -^- 5 - of an inch, or just eighty times that of the 
platina contained in it. 
With portions of the platina wire thus obtained, and succes- 
sively reduced in diameter, I had an opportunity of repeating 
the trials of its tenacity with greater confidence in the justness 
of the estimate, and the results shewed generally (though with 
some accidental exceptions) that the process of wire-drawing, 
which is well known to improve the strength of metals within 
moderate limits, continued also to add something to the tenacity 
of platina, even as far as --g-.J-ir- of an inch, which supported 
grain before it broke ; but the wire on which these expe- 
riments were made, began then to be impaired by repetition of 
the operation ; so that although I afterwards obtained portions 
of it, as small as 3 ^,- 0 of an inch in diameter, it was in many 
places interrupted, and I could place ho reliance upon any trials 
of its tenacity. 
There are some little circumstances in the management of 
these fine wires, which it may be of advantage to describe for 
the assistance of those who would apply them to any useful 
purpose. When the diameter is not less than or 
* lam indebted to my friend Dr. IMarcet for the simple and easy 
method by which the fusion was elfccted. A piece of wire, about six 
ineiics long, liaving been bent to an angle in the middle, one half of 
its length was held in tlie flame of a spirit lump impelled by a curreut 
of oxigeii, and its extremity was thus fused in about half a Hiinutc. 
of 
