702 
MR. FAIRBAIRN’S EXPERIMENTAL INQUIRY 
risk of fire ; and in case of shipwreck, either on rocks or sand-banks, it wall resist 
the heaviest sea, endure the severest concussion, and with proper attention to the 
construction, it may be the means of saving the lives of all on board. It moreover has 
the advantage of bulkheads, which, made perfectly water-tight, not only strengthen 
the vessel, but give greater security to it, and by a judicious 'arrangement in the 
divisions will float the ship under the adverse circumstance of a leak occurring in any 
one of the compartments. These are the qualities and powers of the iron ship ; and 
I trust the present research into the strength and proportions of the material of which 
it is composed, will not only give increased confidence in its security, but will lead 
to an extension of its application in every branch of marine and mechanical archi- 
tecture. 
PART III. 
Resistance of IVrought-iron Plates to Pressure by a Blunt Instrument at right angles 
to the surface of the Plate. 
Irrespective of the experiments made to determine the strength of wrought-iron 
plates and the relative strength of the joints by which they are united, the investiga- 
tion M^ould be incomplete if we omitted another inquiry of equal importance, namely, 
the resistance offered by plates to a crushing force, such as exhibited in the injuries 
received by vessels when stranded on rocks or taking the ground in harbours where 
the surfaces are uneven. 
Almost every person connected with nautical affairs is acquainted with the nature 
of the injuries received by timber-built vessels when placed in circumstances affect- 
ing their stability, or when resting on hard and unequal ground, such as frequently 
occurs in tidal harbours at low water. Such a position is attended with danger under 
every circumstance ; and in order to determine the relative values of the two mate- 
rials, wood and iron, it was considered desirable to institute a similar class of experi- 
ments on both, and thus to afford the means of comparison between them. English 
oak, as the strongest and best material used for the construction of first class vessels, 
was selected for this purpose, and the results obtained from both are given, under 
circumstances as nearly similar as the nature of the experiment would admit. They 
are as follows. 
In each of the experiments the plate was fastened upon a frame of cast iron, 1 foot 
square inside and 1 foot 6 inches outside, its breadth being 3 inches and thickness 
half an inch. The sides of the plates, when hot, were twisted round the frame, to 
which they were firmly bolted. The contraction, by cooling, caused it to be very 
tig^it, and the force to burst it was applied in the centre. This was done in order 
that the force might in some degree resemble that from a stone or other body with 
a blunt end pressing against the side or bottom of a vessel : a bolt of iron, terminating 
in a hemisphere 3 inches in diameter, had thus its rounded end pressed perpen- 
dicularly to the plate in the middle. The results are given in the following Tables. 
