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XX. Experimental Researches on the Strength of Pillars of Cast Iron , and other 
Materials. By Eaton Hodgkinson, Esq. Communicated by Peter Barlow, Esq., 
F.R.S., &§c. 
Received April 22, — Read May 14, 1840. 
WHEN we consider to what extent pillars of iron and of timber are used for the 
support of buildings, and reflect that there are no satisfactory rules by which to 
measure the strength of pillars, it becomes a matter of great importance to obtain 
such rules by means of experiment, and, if possible, to discover the laws on which 
they are founded. A feeling of this kind, heightened by the remarks of Dr. Robison, 
in his Mechanical Philosophy, and by the strongly-expressed opinion as to our 
want of such knowledge by Mr. Barlow*, led me to wish to undertake the in- 
quiry. I mentioned the matter, therefore, to my friend Mr. Fairbairn, who, with 
that liberality which I have experienced from him on former occasions, at once put 
every means of a full investigation into my hands. He expressed a wish that I should 
extend the inquiry to pillars of various kinds, ancient as well as modern ; and leave 
no part of the subject in uncertainty for want of experiments sufficiently varied and 
extensive. Thus freed from restraint, I endeavoured, in my wish to acquire the re- 
quisite information, to forget the expense to which I put my friend, and have made 
every effort to render the experiments at least ample, correct, and useful. The 
pillars on which the experiments were made, were mostly of cast iron, as being the 
material in most general use ; but some were of wrought iron and steel, and others 
of wood. 
In the earlier experiments, the pillars used were uniform cylinders, either with 
their ends rounded, so that the crushing force might pass through the axis, or with 
flat and parallel ends, so that the pillar, when placed between two perfectly parallel 
crushing surfaces, might have its ends completely bedded against them. 
2. The pillars during the experiments were placed vertically, resting upon a flat, 
smooth plate of hardened steel, laid upon a cast iron shelf, made very strong, and 
lying horizontal. The pressure was communicated to the upper end of the pillar by 
means of a strong lever acting upon a bolt of hardened steel, two and a half inches 
diameter, and about a foot long, kept vertical by being made to pass through a hole 
bored in a deep mass of cast iron ; the hole being so turned as just to let the bolt 
slide easily through without lateral play. The top of the bolt was hemispherical, that 
the pressure from the lever might act through its axis ; and the bottom was turned 
* Report to the British Association for the Advancement of Science. 
MDCCCXL. 3 D 
