355 
Mr. Tredgold’s experiments , &c. 
thread fixed over the center of the apparatus, by which the 
scale can be raised or lowered, when the cords on which the 
screw acts are looped on to the cross pin by which the scale 
is suspended. 
To measure the flexure, a quadrantal piece of mahogany 
is fixed to the wooden frame ; two guides are fixed on one 
edge of the mahogany, in which a vertical bar slides, and 
gives motion to an index. The bar and index are so balanced, 
that one end of the bar bears with a constant pressure on the 
specimen, and the graduated arc over which the index moves 
is divided into inches, tenths, and hundredths ; and thou- 
sands are measured by a vernier scale on the end of the 
index. There is a screw at the lower end of the vertical 
bar, by which the index is set to zero, when necessary. 
Plate XX. 
The first trials were made with a bar of blistered steel of 
a very good quality. It was drawn out by the hammer to 
the width and thickness I had fixed upon, and then filed 
true and regular. It was then hardened, and tempered to the 
same degree of hardness as common files. 
The total length of the bar was 14 inches ; the distance 
between the supports 13 inches ; the breadth of the bar 0.95 
inches, and the depth 0.375 inches ; the thermometer varied 
from 55 0 to 57 0 at the times of trial. 
lbs. inches. 
With a load of 54 the depression in the middle was 0.02 
82 - 0.03 
110 - - - - - 0.04 
The last load remained on the bar some hours, but produced 
no permanent alteration of form. 
