206 REPORT—1840. 
A pillar irregularly fixed, so that the pressure would be in the direc- 
tion of the diagonal, is reduced to one-third of its strength. Pillars 
fixed at one end and moveable at the other, as in those flat at one end 
and rounded at the other, break at one-third of the length from the move- 
able end ; therefore, to economize the metal, they should be rendered 
stronger there than in other parts. 
Long-continued Pressure on Pillars. 
To determine the effect of a load laying constantly upon a pillar, 
Mr. Fairbairn had, at the writer's suggestion, four pillars cast, all of 
the same length and diameter; the first was loaded with 4 ewt., 
the second with 7 ewt., the third with 10 ewt., and the fourth with 
13 ewt.; this last was loaded with ;97, of what had previously broken 
a pillar of the same dimensions, when the weight was carefully laid on 
without loss of time. The pillar loaded with the 13 ecwt. bore the 
weight between five and six months, and then broke. 
General Properties of Pillars. 
In the pillars of wrought iron and steel, in Table 12, and in those of 
timber in Table 13, the same laws, with respect to rounded and flat 
ends, were found to obtain, as had been shown to exist in cast-iron. 
Of rectangular pillars of timber, it was proved experimentally that 
the pillar of greatest strength of the same material is a square. 
In square pillars of oak, with flat ends, the strength was expressed 
by this formula, 
Strength in tons = 69 x Si 
where d is the side of the square, and / the length, as before. 
Comparative Strengths of Cast Iron, Wrought Iron, Steel and 
Timber. 
It resulted from the experiments upon long pillars of the same di- 
mensions, but of different materials, that if we call the strength of cast 
iron 1000, we shall have for wrought iron 1745, cast steel 2518, 
Dantzic oak 108°8, red deal ’78°5. 
On a Revolving Balance. By Mr. Loruian. 
The opposing arms of this balance are curved, being formed of two 
spirals, the one situated vertically over the other, and both bending 
round a common centre of movement, which is placed in the pale of 
the upper curve. The spirals diverge from each other near their 
origin, but approach and merge together at their extremes, and thus 
form one continuous curve, which is grooved on its circumference. 
The cords or chains which suspend the receiving scale and counter- 
poise act against each other in this groove—the weight of the scale, 
when hanging from a lengthened radiant of the upper spiral, being in 
equilibrio with the greater weight of the counterpoise when hanging 
