70 ANNUAL OF SCIENTIFIC DISCOVERY. 



shot, having the same velocity when striking the object of resistance, 

 would break as if it had not been hardened at all. 



APPLICATION OF IRON TO THE CONSTRUCTION OF SHIPS OF 

 WAR, AND ITS POWER TO RESIST PROJECTILES. 



In a paper recently published by the eminent English engineer, 

 Mr. W. Fairbairn, the author, in a popular manner, thus sums "up the 

 aggregate of our present knowledge respecting the following topics : 



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

 durability in the construction of ships of war. 



2d. The distribution and best forms of construction to attain this 

 object. 



3d. The properties of iron best calculated to resist the penetration 

 of shot at high velocities. 



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

 mechanical, architectural, or shipbuilding construction, it is essential 

 that the engineer ci v 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 combination of the parts, before we can arrive at satistactory 

 results ; and to effect these objects, the naval architect should be con- 

 versant 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 



Yorkshire Iron is 24 50 tons. 



Derbyshire " 20.25 " 



Shropshire " 22.50 " 



Staffordshire " 20.00 " 



Strength of Riveted Joints. The architect, having fortified him- 

 self with the above facts, will be better able to cany 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 

 uniformity 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 riveted joints of plates to the plates 

 themselves. These, according to experiment, give the following re- 

 sults : 



Taking the cohesive strength of the plate at ...... 100 



The strength of the double-riveted joint was 70 



And the single-riveted joint 56 



These proportions apply with great force to vessels requiring close 

 riveting, such as ships and boilers that must be water-tight, and in 

 calculation it is necessary to make allowance in that ratio. 



Strength of Ships. Of late years it has been found convenient to 

 increase the length of steamers and sailing vessels to as much as eight 



