and Strength of Materials. 253 
It appears to me that such experiments as 
these shew very satisfactorily the law that re- 
gulates the actions of the particles upon one 
another: But whether the same conclusion 
would be drawn from stretching the fibres of 
so irregular a thing as a piece of timber, and 
especially when near their fracture, is not 
quite so plain. We havescarcely any means 
of doing that but by bending it ; and then, if 
we fasten one end of a beam firmly in a wall, 
and hang weights at the other, the strain 
will be complex : the piece will be subject to 
extensions and compressions the laws of which 
may change, together with the situation of 
the neutral line; and the only conclusion we 
can draw is, that the aggregate of the exten-' 
sions and compressions it sustains, leaves a 
deflection from its primitive form, which is 
nearly in proportion to the force. 
23. But it occurred to me, that if we 
could prevent compression taking place by 
furnishing an artificial fulcrum on the side of 
the beam, we should by bending it have all 
its fibres in a state of dilatation, and that in 
proportion to their distance from the fulcrum. 
With this intention we took two pieces of 
iron, each one inch broad, :th inch thick, 
and from a foot to 18 inches long. The end 
of one of them was sharpened a little to fit 
