1S2 ML’maj'lcs on Professr Hanstcen’’^ 
ments led liim to adopt the same opinion : some even contended 
tliat it was not proportional to any power of the distance. And 
though Mayer, in an unpublished paper read before the Society 
of Gottingen in 1760, and Lambert a few years later, asserted 
the inverse square of the distance to be the true expression of 
this law, their statements seem rather to have proceeded on ge- 
neral and somewhat vague deductions, than on decisive facts ; 
and Coulomb (1786) was the first who established this principle, 
on grounds at all satisfactory.' By means of the simple instru- 
ment which he invented, and named the Torsion-balance % he 
was enabled to measure, with great precision, the force necessary 
to make a magnetic bar, horizontally suspended, deviate by any 
number of degrees from the position assigned to it. Having by 
this means verified the discovery of Lambert, that the effect of 
the terrestrial magnet is proportional to the sine of the angle 
which its meridian makes with that of the magnet acted upon 
by it ; and having farther ascertained, that a magnetised steel 
wire, 24? inches long and 1 J line in diameter, required 35° of 
torsion to force it one degree from the magnetic meridian of the 
earth, he took another wire, of equal dimensions, and the same 
degree of magnetism, and placing it vertically in the magnetic 
meridian, so that its extremity or pole would have intersected 
the homologous pole of the horizontal wire, (had no influence 
existed between them, or their poles not been homologous), at 
the distance of an inch from the end of each, — he observed the 
force of torsion necessary to overcome certain quantities of their 
mutual repulsion. , It was found, that the vertical wire at first 
repelled the horizontal one 24 degrees ; that three circles of tor- 
sion, or three complete turns of the micrometer, brought the 
latter within 17 degrees of the former; and, lastly, that eight 
circles brought the wires v/ithin 12 degrees of each other. Add- 
ing to each of these results, the effect of the terrestrial magnet, 
already estimated at 35° of torsion for each degree of devia- 
* It consists merely of a very slender wire, generally of silver or copper, by 
which the magnetic bar to be operated on is suspended in a horizontal direction. 
The suspending wire is furnished with a micrometer, to indicate the number of 
turns, or the quantity of torsion it has sustained. The force is proportional to the 
ai:G of torsion. 
