VOL. XLI.] PHILOSOPHICAL TRANSACTIONS. 343 



Let US suppose a row of round particles touching one another only in the 

 points c in a line from a to b, fig. Q. It is plain, from what philosophers have 

 shown concerning the attraction of cohesion, that on the least shake or alteration 

 of the position of a straight line, these particles will run together, and form a 

 sphere, in which the globules will have more points of contact. But if these 

 particles have poles like magnets, in the opposite places marked n s, so that all 

 the poles n, n, n, &c. repel one another ; and all the poles s, s, s, &c. likewise 

 repel one another, the line a b will continue straight ; for if by any force the 

 same line b a be put into another position, as into the curve b a, then the poles 

 n, n, &c. being brought nearer together, while the poles s,s, &c are further 

 asunder, will repel one another more strongly, and so hinder the globules from 

 running together towards the concave part ; and the spring, left to itself, all 

 this while supposing one end, as b, b, or |3, fixed, will restore itself, throwing 

 its end a back to A, and so on to a, by the first law ; then, being in the po- 

 sition « (3, the poles s, s, &c. are brought nearer together, whose repulsion, thus 

 increased, throws back a to a, and so on forward, the line of particles perform- 

 ing several vibrations round b. 



May not a spring of steel, or other springs, consist of several series of such 

 particles, whose polarity and attraction acting at the same time, will show 

 why such bodies, when they have been bent, vibrate, and restore them- 

 selves ? 



If we take a plate of steel, and make it so hot till it looks white, and then 

 immediately quench it, we thereby fix the metal in a state very near fluidity, 

 so that the particles which the fire had almost brought to roundness, have but 

 a very small contact ; as appears by the fragility of the steel thus hardened, 

 which breaks like glass, and has a short grain. Steel, thus hardened, is highly 

 elastic ; for what workmen call hard, is the most elastic ; as appears by the 

 congress of high-hardened steel balls, which return, in their rebound, the 

 nearest to the place we let them fall from ; and, next to glass, have the quickest 

 elasticity of any thing we know. 



That we may not be thought to have given an imperfect account of the elas- 

 ticity of a steel spring, because such a one as we have described wants tough- 

 ness, and will immediately fly, when bent to any degree ; we must beg leave 

 to consider further the properties of the round particles, or little spheres, of 

 steel, in which we have supposed a polarity. 



Let us suppose a B, fig. 10, to be two little spheres or component particles 

 of steel, in which, at first, we will suppose no polarity, but only an attraction 

 of cohesion. Then, whether the particles have their contact at c, d, e, n, or 

 at i, t, s, their cohesion will be the same ; and the least force imaginable will 



