INTO THE STRENGTH OF WROUGHT-IRON PLATES. 
701 
The figures 2, T5, 4*5, 6, 5, &c. in the preceding Table are multipliers for the dia- 
meter, length and distance of rivets, also for the quantity of lap allowed for the 
single and double joints. These multipliers may be considered as proportionals of 
the thicknesses of the plates to the diameter, length, distance of rivets. See. For ex- 
ample, suppose we take three-eighth plates and required the proportionate parts of 
the strongest form of joint, it will be — 
•375x2 = '750 diameter of rivet, f inch, 
•375X4^=r688 length of rivet. If inch. 
•375X5 =1-875 distance between rivets, if inch, 
•375 X 5|=:2-063 quantity of lap, 2 inches. 
•375x55—3-438 quantity of lap for double joints, 3^ inehes. 
•75, r68, 1-87, 2-06 and 3-43 are therefore the proportionate quantities necessary to 
form the strongest steam- or water-tight joints on plates three-eighths of an inch 
thick. 
In the preceding pages I have endeavoured to investigate almost every circum- 
stance having a practical bearing on the question of the strength of rolled plates, and 
the best methods of uniting them together. In conclusion, I would venture a few 
remarks on the value and judicious use of this material, in its adaptation to ship- 
building, and other purposes to which it may be successfully applied. It is not my 
intention to enter into the question as to whethei' wood or iron be the preferable 
material, as a number of circumstances, such as cost, durability, &c., must be con- 
sidered in order to form a correct decision. 
I would however observe, that in ship-building alone, it appears from the facts 
already recorded, that iron is very superior in its powers of resistance to strain ; it is 
highly ductile in its character, and easily moulded into any required form without 
impairing its strength. It is also stronger in combination than timber, arising from 
the nature of the construction, and the materials composing the iron ship become 
a homogeneous mass when united together, forming as it were a solid, without 
joints, and presenting as a whole the most formidable powers of resistance*. These 
are some of the properties which appear to distinguish iron from other materials, and 
which give it an ascendency of combined action, which cannot be obtained in the 
union of timber however ingeniously conlriv^ed. It moreover possesses the property 
of lightness along with strength ; in fact, its buoyancy, strength and durability con- 
stitute the elements of its utility in the innumerable cases to which it may be applied. 
In ship-building it possesses other advantages over timber. Its hull is free from the 
* Since the above was written we have had many examples of tl\e enormous strength of iron ships, and 
amongst others we may instance an iron vessel which took the ground with nearly one-half of her length at the 
stern hanging over a shelf for a whole tide ; another, the Vanguard iron steamer, which for several hours 
(under the action of a heavy surf) was beating upon sharp shelving rocks without going to pieces ; and lastly, 
the Great Britain steam-ship, which was stranded in Dundrum Bay, and resisted the force of the winter storms 
for many months. 
