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That this does take place is evident, from the fact that both 
wooden and iron vessels have been known to founder by 
giving way and breaking asunder. Circumstances may at 
any time arise when the danger from this source becomes 
greatly increased. The vessel may be cast ashore, and with 
the receding of the tide may be left suspended partially out of 
the water, and remain supported at only one or two points in 
her length, by ledges of rock. Such cases have occurred, and 
it has become doubtful, whether our present construction of 
iron vessels enables them to withstand the shocks and impacts, 
to which in such a case they may be subjected. 
This is not the first time I have applied myself to the 
inquiry, for the purpose of ascertaining, in the first place, 
what is the transverse strength of vessels as now constructed ; 
and next, whether the builders of iron ships have been guided 
in their construction by right principles, and have obtained 
the greatest strength with the smallest quantity of material. 
In pursuing this investigation, I have come to the conclusion 
that our present iron vessels are dangerously weak when 
exposed to strains of the kind I have indicated ; and I believe 
that this defect of construction may be remedied by a more 
careful attention to correct principles of proportion, without 
in any great degree increasing the weight of the vessel. 
To ascertain the strength of our present ships, I have 
supposed them to be placed in the extreme position of danger 
to which they are ever likely to be exposed ; that is, supported 
at the centre of the vessel on some rock with the ends freely 
suspended. In this position an iron vessel is, in fact, a 
wrought iron hollow girder, and we may apply the simple 
formula, JV = — which we ascertain the strength of 
such constructions. 
If we take vessels of the great length of which they are 
now made, we shall find that they are far too weak along the 
deck to resist the force of tension, to which, in the position 
