and Strength of Materials. 267 
tre of the forces exerted by the fibres from 
the fulcrum or iron,—But the process is 
omitted as uninteresting. 
It will then be unnecessary to use any cor- 
rection for the dilatation of the iron in these 
experiments ; and as it is improbable that its 
compressions will be much greater than its’ 
dilatations from equal forces, it will be un- 
necessary too to correct for what compression 
it may have sustained in the former. 
NEUTRAL LINE. 
31. My next object was to find the position 
of the neutral line, aud that before the piece 
was overstrained, since then the extensions 
and compressions are nearly as the forces. 
With this intention I formed an arc of a 
circle, the greatest a piece of yellow 
pine one inch deep would bear without de- 
stroying its elasticity, and, bending upon it 
the pieces of wood intended to be operated 
on, obtained by admeasurement the exten- 
sions of the outer sides, and the contractions 
sustained by the inner ones. 
The method I used was this: I took a slip 
of tin upwards of 9 feet long, and whose 
thickness was not more than th or 7,th of 
aninch. It had one end divided into parts 
of an inch, and the other nailed to the ex- 
