492 Mr, fV. Fairhairn oti the Properties of Iron, [May 9, 



are no longer applicable to the wants of the state ; and I am clearly of 

 opinion that we cannot afford to trifle with so important a branch of the 

 public service as to fall behind any nation, however powerful and efficient 

 they may be in naval construction. Having satisfied ourselves that 

 this desideratum must be attained, at whatever cost, I shall now 

 endeavour to point out such facts as in ray opinion relate to the changes 

 that are now before us, and simply endeavour to show — 



1st. The description of iron best calculated to secure strength and 

 durability in tlie construction of ships of war. 



2nd. The distribution and best forms of construction to attain 

 this object ; and, 



Lastly. The properties of iron best calculated to resist the pene- 

 tration of shot at high velocities. 



Properties of Iron. — If we are desirous to attain perfection in 

 mechanical, architectural, or ship-building construction, it is essential 

 that the engineer or architect should make himself thoroughly ac- 

 quainted with the properties of the materials which he employs. It is 

 unimportant whether the construction be a house, a ship, or a bridge. 

 We must possess correct ideas of the strength, proportion, and combina- 

 tion of the parts, before we can arrive at satisfactory results ; and to 

 effect these objects the naval architect should be conversant with the 

 following facts relating to the resisting powers of malleable and rolled 

 iron to a tensile strain. 



The resistance in tons per square inch of — 



Yopkshire Iron is . . . 24*50 tons. 



Derbyshire „ . . . 20*25 „ 



Shropshire „ . . . 22-50 „ 



Staffordshire „ . . . 20-00 „ 



Strength of Rivetted Joints. — The architect having fortified him- 

 self with the above facts, will be better able to carry out a judicious 

 distribution of the frames, ribs, and plates of an iron ship, so as to meet 

 the various strains to which it may be subjected, and ultimately to 

 arrive at a distribution where the whole in combination presents uni- 

 formity of resistance to repeated strains, and the various changes it has 

 to encounter in actual service. 



There is, however, another circumstance of deep importance to the 

 naval architect, which should on no account be lost sight of, and 

 that is, the comparative values of the rivetted joints of plates to the 

 plates themselves. These, according to experiment, give the following 

 results ; — 



Taking the cohesive strength of the plate at . 100 

 The strength of the double-rivetted joint was 



found to be . . . . .70 



And the single-rivetted joint , , , 6Q 



