710 
MR. FAIRBAIRN’S EXPERIMENTAL INQUIRY 
This experiment shows the superior quality of wrought-iron beams in giving timely 
notice before fracture ; it further exhibits weakness on the top sides of the beams, a 
circumstance requiring great attention in their construction, which in some recent 
experiments, instituted for attaining the section of greatest strength, have been 
strikingly developed*. 
In the preceding experiments, we have endeavoured to compare the strengths, as 
well as the weights of the beams or frames which form the ribs of ships. As regards 
the strengths with equal weights, it is in favour of oak; but the circumstance of 
the fastenings by rivets in the sheathing being so much superior to those of timber, 
the iron ship-builder is enabled to dispense with one-half the number of frames, 
and consequently a great reduction of weight is elfected and more strength obtained 
in the vessel as a whole, than could possibly be accomplished in the timber-built 
ship, however ingenious the construction or the arrangement and distribution of the 
material. The very act of caulking the joints of a wooden vessel has a tendency to 
loosen the fastenings, whereas, in the iron ship, there are no actual joints, for the whole 
being bound together en masse, the same, or nearly the same, strength is obtained as 
if the whole ship were composed of solid plates and ribs. 
The best sectional form of beams for the decks of ships is probably that exhi- 
bited in Table XX., which, along with the box beam of the annexed form 
for supporting the shafts and paddle-boxes of steamers, is that generally 
used in the construction of vessels of this description. Other forms have 
been adopted, particularly those suggested by Mr. Kennedy of Liver- 
pool, alluded to in the Appendix. 
Having carefully investigated the different properties of wrought iron in its varied 
forms of construction, and conceiving that the results obtained from the experiments 
may be useful in a variety of circumstances connected with the useful arts, I have 
endeavoured to collect them in the abstract, in order that the practical builder and 
engineer may the more readily ascertain the comparative value of the different forms 
of beams, the properties of the material, and their adaptation to any particular con- 
struction in which he may be engaged. Should further information be required, we 
must then refer to the experiments, in which will be found the facts more in detail, 
and which are probably better calculated to satisfy the inquiring mind and to effect 
that conviction essential to success. 
I have not attempted any inquiry into the laws of oxidation, the adhesion of bar- 
nacles and marine vegetation, and the means necessary to prevent such evils. This 
is a subject which does not come within the province of the present inquiry, and 
more properly belongs to that of the chemist. I would however briefly notice, that 
in the whole of my experience I have had little to complain of from the effects of 
oxidation, as that destructive process, as regards iron, appears to be greatly mitigated, 
if not almost suspended, by constant use, and under the influence of vibratory action 
the operation appears to be rendered nugatory, if it does not entirely cease, and that 
* See my work on the Construction of the Britannia and Conway Tubular Bridges. 
4 
