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MR. HODGKINSON’S EXPERIMENTAL RESEARCHES 
months longer. The lengths of the latter specimens were, in some instances, only one 
inch, which reduction would increase the strength a little. But the great difference 
frequently seen in the strength, as given by the two columns, shows strongly the effect 
of drying upon wood, and the great weakness of wet timber, it not having half the 
strength of dry. The strength of short columns of the same material I have shown 
to be directly as the area of the section*. This seems easy to conceive, as bodies of 
the same nature always become crushed by sliding off in an angle, which is nearly 
constant ; the height of the wedge, which would slide off, being in timber usually 
about half the diameter, or thickness of the specimen. 
Relative Strength of Long Pillars of Cast Iron, Wrought Iron, Steel, and Timber. 
68. To compare the strengths of pillars, of the same size, in the different materials 
used in the preceding experiments, I have computed, by the rules used for cast iron 
(Art. 36-38.), the strength of a pillar, of the same diameter and length, in each body, 
taking the results from the longest pillars, in order that they may not be crushed (as 
described in Art. 6.) by the breaking weight. The relative strengths are as below : 
Calling the strength of cast iron 1000, we have for wrought iron 1745, cast steel 
2518, Dantzic oak 108*8, red deal 78*5. These numbers, except the last, are all com- 
puted from the pillars with rounded ends. 
* Transactions of the British Association, vol. vi. 
