852 
ME. HODGKINSON’S EXPEEEVIEXTAL EESEAECHES 
6 inches long, acting (usually) with a leverage of 8' 4 upon the upper end of a strong bolt, 
which moves in a cylinder, just fitting it and keeping it always in the straight line of 
its pressure. The top of the bolt is rounded, so that the pressure may act through the 
axis, and the bottom is fiat, and made horizontal, that it may press on the top of a ver- 
tical pillar, enclosed in a strong box, as before. See Plate XXXI. 
The present experiments, and others in progress, were undertaken at the suggestion 
of Mr. Eobeet Stephenson, M.P., F.E.S., who knew that I had several experimental 
researches unfinished. He has generously contributed £200 towards the expense of 
the inquiry, and the Eoyal Society has added £200*. By the kind peiTuission of the 
Council of University College, London, my apparatus has been set up at the College, 
and the experiments made there. 
I have in the present research broken only larger pillars than before, having had them 
cast 10 feet long, and from 2^ to 4 inches in diameter, solid and hollow. The fii’st series 
includes twenty pillars (twelve of 10 feet long, and eight shorter ones cut out of them); 
the whole of these were supplied by the proprietors of the Low Moor Iron-works, for 
which no charge has yet been made f. The u’on of which these, with five exceptions, 
were made, was Low Moor iron. No. 2. The former research of 1840 was from Low 
Moor iron. No. 3 ; and the difference of the two is not very great, though the No. 2, as 
now used, is somewhat stronger than the other to bear a strain as a long pHlar (p. 864), 
though softer than it and more easily crushed. The results of these experiments have 
been applied to the formulae in my former research, which have undergone no change, 
except in the constants. 
The former researches, and the formulae to which they were reduced, had been applied 
to pillars of Low Moor iron only, with one exception ; but though we could compute by 
them the strength for Low Moor iron, we had no eUdence as to what were the relative 
strengths of pillars of the irons of the kingdom in general ; and, at my request, Messrs. 
Easton and Amos have had cast for this purpose twenty-two sohd pillars, each 10 feet 
long and 2 ^ inches in diameter, of eleven kinds of iron, making thirteen kinds with two 
I have had from Low Moor. The comparison of the breakiag weights of these pillars 
shows that the strengths of the irons vary at least as 2 to 3, and then* crushing strengths 
as 5 to 9 nearly l|;. 
In carrying out the experiments, in taking the dimensions, and applying the results 
to the formulae in my research above mentioned, I have had the assistance of ]\L-. John 
Beidge, M.A., of University College, my health and eyesight not being sufficient to 
enable me to bear the labour alone. 
* Since finishirjg the experiments in the present research, except those contained in the short Appendix, 
another ^6100 has been contributed by the Eoyal Society, and sElOO more by Mi-. Stepheksox, with which 
I am making experiments on pillars of timber, &c. 
t A good balk of Memel timber was likewise sent gratuitously for experiment by the late IMi-. Thoxias 
C uBiTT, of Thames Bank, but his death prevented me haidng the power to thank him. His executors have 
liberally sent other timber for the purpose. 
J The pillars were cast 12 feet long, to increase their soundness, and afterwards cut to 10 feet long. 
