Suspension of the Magnetic Needle. 83 
by varnish to the north pole of this wire, which served more 
accurately to distinguish its position opposite to a bit of ivory 
marked with degrees. This wire was turned round as before, 
more than a thousand times ; yet when suffered to rest, it stood 
exactly at the same degree, the twist of the spider’s thread 
having produced no sensible deviation. 
EXPERIMENT III. 
A fine spider’s thread was fastened to the spindle of a wheel 
used for spinning flax ; the wheel was placed so that the 
spindle and thread might hang perpendicularly. To the end 
of the thread, which was about two inches and an half long, 
was fastened, by its smaller end, one fibre of the feather of a 
goose-quill: the lower end of the fibre rested upon a book. 
The wheel was turned round till the spindle had made above 
18,000 revolutions. During this time the spider’s thread gra- 
dually became about one inch shorter, yet all this twisting did 
not cause the fibre to turn round when raised from the book. 
On turning the spindle about 500 times more, the thread broke, 
apparently by twisting. 
Several twisted spider’s threads were viewed by means of a 
very good lucernal microscope, made by Mr. Adams, without 
being able to perceive any signs of twist, except where it was 
doubled, and which appeared like hairs growing out of the 
thread : yet the twist may be distinctly seen by the naked eye, 
in the sunshine, in some threads to be found amongst trees, 
where the spider has probably been turned round by the wind 
during its descent from one branch to another. 
M 2 
