684 
MR. FAIRBAIRN’S EXPERIMENTAL INQUIRY 
Here it will be observed that the difference between the strength of the Low Moor 
plates in their resistance to a tensile strain, when compared with bar iron, is incon- 
siderable ; but taking the mean of the other irons, viz. the Derbyshire, Shropshire 
and Staffordshire, there is a falling off in the strength of about 21 per cent., the ratio 
being in favour of bar iron as ]'035 : '8209. 
In treating of the strength of iron, it may be useful to compare the foregoing expe- 
riments on the tensile strength of plates with those of a similar description on timber. 
On this subject I feel the more desirous of establishing a comparison, as the two kinds 
of material are now applied to similar purposes, such as ship-building and other con- 
structions, and the question becomes every day more important as to which of the two 
materials is the best. There is every reason to believe that the advocates of improve- 
ment would arrange themselves on the side of iron, and those for the “ wooden walls ” 
would be equally zealous on that of timber. This is however a question which time 
and experience alone can determine, and conceiving that our knowledge of the pro- 
perties of iron, as a material for ship-building, is far from perfect, we may safely leave 
its final decision to the evidence of experimental research, and a more extended ap- 
plication of its practical results. 
When we attempt a comparison of the value of one material, in its application to a 
specific purpose, with that of another material similarly applied, the comparison is only 
correct when the two materials are placed in juxtaposition, or when they are contrasted 
under the same circumstances as to the trials and tests to which they are respectively 
subjected. Now in this comparison I am fortunate in having before me the able ex- 
periments of Musschenbrock, Buffon, and those of a more recent date on direct co- 
hesion by Professor Barlow of Woolwich. I have selected from the experiments of 
the latter those which appear to approach most nearly to the present inquiry; and 
impressed with the conviction of their having been carefully condueted and being 
from English timber, I attach the greatest value to them. 
According to Musschenbrock’s, the strengths of direct cohesion per square inch of 
the following kinds of timber are as follows : — 
Locust-tree 
lbs. 
. . . 20,100 
Pomegranate 
lbs. 
9750 
Locust-tree . . 
. . . 18,500 
Lemon 
. . . 9250 
Beech and oak . 
. . . 17,300 
Tamarind. . . . 
. . . 8750 
Orange .... 
. . . 15,500 
Fir 
. . . 8330 
Alder .... 
. . . 13,900 
Walnut .... 
. . . 8130 
Elm . . . . . 
. . . 13,200 
Pitch pine . . 
. . . 7630 
Mulberry . . 
. . . 12,500 
Quince .... 
6750 
Willow .... 
. . . 12,500 
Cyprus .... 
. . . 6000 
Ash 
. . . 12,500 
Poplar 
. . . 5500 
Plum .... 
. . . 11,800 
Cedar 
. . . 4880 
Elder .... 
. . . 10,000 
