OF THREE LARGE LOADSTONES. 393 
but as a loadstone is very apt to be injured by being struck 
forcibly, it might be hazardous to make the trial. 
Before concluding this paper, I may take notice of an 
imposition which was, about three years ago^ attempted to 
be kept up upon the prosecutors of science in different 
parts of the united kingdoms by a needy shoemaker, as 
this disgraceful fraud was first exposed by means of the 
largest of the magnets just explained. This individual 
pretended he had discovered a black substance which did 
not conduct magnetic energy through it, and he wished it 
to appear, that when this substance was made to come be- 
tween a steel beam and a magnet, the power of attraction 
was at least lessened, if not altogether stopped. He placed 
machinery in such a situation as not to be observed, and, 
with the assistance of a few falsehoods, which he found 
very useful in raising the curiosity and extorting the cha- 
rity of credulous visitors, he tried to induce a belief that a 
pendulum was then moving a clock, and had continued 
to do so for six months, without any other exciting 
power than two small magnets. This is shewn in fig. 7. 
A B are the two supposed non-conductors of magnetism, 
affixed to the opposite ends of a beam moving on its centre; 
C D are the two magnets, which were said to attract alter- 
nately the end E of the pendulum EF. At the commence- 
ment of the motion of the pendulum, it was said that one 
of the pieces of the black substance, say A, was moved from 
between the magnet C and the pendulum ; this enabled 
the attraction between C E to take place, and cut off the 
attraction between D E ; and this is the state in which the 
figure on the plate is drawn. But as E approaches nearer 
to C, so as to present the actual contact of C E, then A 
moves up, and entirely cuts off the effect, and at the same 
time B leaves the power of D in full action ; therefore E 
