REVIEWS. 
101 
In reading this description of the unromantic attributes of a modern 
mail-clad vessel, some of our readers will probably deplore the entire 
disappearance of the poetry, hitherto associated with the navy, and may 
perhaps be reminded of Byron’s lines : — 
tc She walks the waters like a thing of life, 
And seems to dare the elements to strife. 
Who would not brave the battle fire, — the wreck, 
To move the monarch of her peopled deck ! ” 
and then turn somewhat deprecatingly to that most graphic account of 
the Monitor as “a Yankee cheese-box on a raft,” which is said to give a 
better idea of her appearance than any of the engravings which have been 
published. In our own armour-clad vessels, the aesthetic element has not 
hitherto been sacrificed to so great an extent ; but Captain Coles’s cupola 
ships which are in progress will closely accord with the American type. 
The questions dealt with in the pamphlet relate to the quality of iron 
most suitable for armour-plates, and the laws of resistance of such plates 
to projectiles, as determining the conditions under which they should be 
applied in naval construction. 
Of the three materials, cast iron, wrought iron, and steel, the first is 
manifestly defective in all the qualities requisite ; but the choice between 
the other two is more difficult. Tenacity, or cohesive force and tough- 
ness, or capability of yielding to a blow without fracture, are pointed out 
as the qualities most desirable. The tenacity of steel is twice as great as 
that of wrought iron ; but Mr. Fairbairn implies that in the trials with 
ordnance it has proved inferior, even when so soft as to contain only 0 - 25 
per cent, of carbon. If this be the case, our French rivals have made a 
mistake in clothing La Gloire with steel-faced plates. 
It is interesting to remark, that chemistry has aided the engineer in 
this inquiry, the absence of carbon being one of the most available indi- 
cations of the value of an armour-plate. The data which Mr. Fairbairn 
quotes show also that the most minute excess in the proportions of sul- 
phur, phosphorus, and silicon, in Dr. Percy’s analyses, correspond exactly 
with deteriorations of strength in his own experiments on the same plates, 
and with inferiority in resistance to projectiles in the trials at Shoebury- 
ness. The purer the iron, therefore, the greater its value for defence. 
This result might have been anticipated, but it is none the less interesting 
to find it clearly demonstrated in independent researches. 
In defensive constructions the engineer has to comply with entirely new 
laws of resistance. Hitherto he has almost universally dealt with slowly- 
applied forces, which it was convenient to regard as dead (or statical) 
pressure. But projectiles have a velocity of 1,100 to 2,000 feet per 
second, and inflict an injury wholly incommensurable with the statical 
resistance of the plates. Statical forces acting for an indefinite period are 
regulated by one law ; sudden and almost instantaneous impact, by an 
entirely different one. It is in consequence of a misconception on this 
point that much of the discrepancy of opinion on the subject of iron 
armour has arisen. And an adequate return will have been made to 
engineers for the service they have rendered to naval construction if it 
