386 
MR. HODGKINS ON’S EXPERIMENTAL RESEARCHES 
flat to rest upon the pillar. The bottom of this bolt, and the shelf on which the 
pillar stood, were necessarily kept parallel to each other; for the mass through 
which the bolt passed, and that on which the shelf rested, were parts of the same 
large case of iron, cast in one piece, and so formed as to admit shelves at various 
heights, for breaking pillars of different lengths. The case had three of its four 
sides closed; circular apertures were, however, made through them, that the experi- 
menter might observe the pillar without danger. 
Fig. 1, Plate XIII., will show more clearly the nature of the apparatus, and the 
manner in which the experiments were made. Thus A B is the lever, about fourteen 
feet long, generally acting with a leverage of from four to seven ; C D is an iron 
frame-work, in which the fixed end of the lever is placed, and in which it turns as on 
a pivot, the frame C D being fixed firmly in a strong heavy wall E F, part of which 
is imagined in the drawing to have been removed, to show the fixings and apparatus ; 
G is the steel bolt on which the lever acts ; II the socket through which it passes ; 
IT I K the iron case admitting shelves as P, at different heights, for pillars of different 
lengths not exceeding five feet ; L M an additional part to be attached to the box 
H I K, for pillars of greater length ; N O is one of the pillars resting upon the shelf 
P, and pressed upon by the pin G ; Q is the weight, which could be removed to any 
part of the lever, and increased or diminished at pleasure ; or entirely taken off the 
pillar, at any time, by means of the winding apparatus. 
Experiments. 
3. In order to ascertain the laws connecting the strength of cast iron pillars with 
their dimensions, they were broken of various lengths, from five feet to one inch ; 
and the diameters varied from half an inch to two inches, in solid pillars ; and in the 
hollow ones, the length was increased to seven feet six inches, and the diameter to 
three inches and a half. My first object was to supply the deficiencies of Euler’s 
theory of the strength of pillars*, if it should appear capable of being rendered prac- 
tically useful ; and, if not, to endeavour to adapt the experiments so as to lead to 
useful results. 
4. As the results of the experiments were intended to be compared together, it was 
desirable that all the pillars of cast iron should be from one species of metal ; and the 
description chosen was a Yorkshire iron, the Low Moor, No. 3. The pillars were 
mostly made cylindrical, as that seemed a more convenient form in experiments of 
this kind than the square ; for square pillars generally break anglewise. The expe- 
riments, in the first table annexed, were made on solid uniform pillars, rounded at 
the ends, that the force might pass along the axis ; and the metal was cast in dry 
sand, to obtain, as far as possible, uniformity in its texture. In the second table, the 
pillars were uniform and cylindrical, as before, but had their ends flat and at right 
angles to the axis. The pillars were from the same models as before, but were cast 
* Berlin Memoirs, 1757, Petersburg!! Commentaries, 1778. 
