178 ENQUIRY INTO THE STRENGTH AND 
It appears from authors, who have recently 
written on the strength of materials, that all 
crystalline or tenacious bodies, subjected to a 
transverse strain, have one of their sides elon- _ 
gated, whilst the other is compressed; they are 
also agreed as to a point, called the neutral 
point, round which revolve the opposing forces of 
tension and compression. In our experiments it 
is evident, as the deflection increases, the atoms 
or crystals on the lower side of the bar must be 
separated, and those of the upper side brought 
nearer together.* Mr. Hodgkinson in his paper 
on the strength of iron beams, (Manchester 
Memoirs, vol. 5, second series, page 409,) states 
the following proposition—‘ Suppose a beam 
horizontal, with one end firmly fixed in a wall, 
and a weight hung at the other, it will bend ; 
but it is evident that could not take place, 
except by the lengthening of the top parts, 
by the compression of the bottom, or by both. 
Now both of these actually take place ; and 
‘hence there is some intermediate point or line 
between the top and bottom of the beam, where 
the particles are neither extended or compres- 
sed. This line may properly be called the 
* This has only lately been admitted, bodies have hitherto 
been considered incompressible. 
