Perhaps the greatest war invention of modern times was the British battleship Dreadnought.

Of course, there have been battleships for centuries. In history we read of fleets consisting of so many "ships of the line" or in other words "line-of-battle" ships, meaning ships which were considered capable of taking their place in "line of battle," as distinguished from "frigates" which correspond to the modern "cruiser."

The "line-of-battle" ships were stout and strong with plenty of guns. They went into the thick of the fight, since they were capable of giving and receiving hard blows, while the lighter frigates hovered around seeking an opening to use their higher speed to cut off stragglers or to prey upon merchant ships.

Although so different in form and material that a sailor of the old days, could he revisit the earth, would not recognize them, the battleships of to-day are the real descendants of the "line-of-battle" ships of those times. They are stout and strong, with the heaviest guns, capable of giving and taking the hardest knocks, and it is they who form the backbone of the fleet. As we saw in the accounts of the battle of Jutland, the German Fleet tackled our cruisers and lighter vessels but discreetly withdrew when the battleships came up.

Looked at in another way, we may say that a battleship is a floating fortress. Its speed is not great, when compared with other ships, but it is constructed to carry enormous guns. It is also armoured with steel plates of great thickness and of special hardness placed upon the outside of the hull so as to cover its vital parts and protect them from the shells of the enemy. Its chief function, we may say, is to carry its guns: to enable it to do this with safety, it is armoured: and to enable it to get to grips with its enemies it has engines and boilers. Those are the three features of greatest importance in a battleship, its guns, its armour and its engines. All else is of minor importance.

It is strange to think how short a time the iron or steel ship has been with us. In the American Civil War, for instance, only about sixty years ago, the battleships were made of wood. It was during that war that Ericcson thought of the idea of putting iron plates to protect the sides of a ship from the hostile shots, and from that improvised armouring of a wooden ship has arisen the iron-clad or, more correctly, steel-clad monsters of to-day.

It is just about fifty years ago since the last iron-clad wooden battleship was launched for the British Navy. Her name was Repulse, and she took the water in 1868. With a tonnage of 6190 and a horse-power of 3350, she had a speed of 12 knots. Her armouring of iron was in parts 4½ inches and in other parts 6 inches thick, while she carried 20 guns of sizes which to-day would seem mere toys. If all her guns were discharged together she would throw a total weight of 2160 lbs. of projectiles.

Now, for comparison, let us take a modern battleship, the Orion, for example. The tonnage is 22,680, the horse-power 27,000.

She is more than twice the length of the older ship and is armoured with steel 12 inches thick. Her 10 large guns, each 13½ inches in diameter, if fired together (as I once heard them, like thunder, though 10 miles away) throw a weight of 12,500 lbs.

From this we see the wonderful growth in size, speed and in hitting power during the comparatively short period of fifty years. But there is a more striking comparison still.

The Repulse's guns threw 2160 lbs. and the Orion's throw 12,500. But that takes no account of the energy with which the weight is thrown. A tennis ball hit hard, might really contain more energy and do more damage to anything it hit than a cricket ball thrown gently, which illustrates the fact that in comparing the power of guns we need to consider something more than the mere weight of the projectiles. To arrive at a real comparison we take the weight of the projectiles in tons and multiply it by the speed at which they leave the guns in feet per second. And we call the answer so many "foot-tons."

Now the energy of the Repulse thus reckoned comes to just under 30,000; that of the Orion to just under 690,000. The Orion can hit twenty-three times as hard as could its forerunner of only fifty years ago.

Since the Repulse all our battleships have been built of wrought iron or mild steel. Speaking generally, there was a steady development in size and horse-power and in speed until 1906, in which year there was launched the world-famous H.M.S. Dreadnought. Previously no battleship had been faster than 19 knots: she was designed for 21 knots. Her tonnage was 17,900, exceeding by more than 1000 tons anything that had gone before. But the great change was in the guns. Pre-Dreadnoughts had, or one ought to say "have" for there are still many in existence, four of the biggest guns, a number of medium-sized guns and a still larger number of smallish guns intended for the purpose of keeping off torpedo craft and such small fry.

At one stroke Lord Fisher, who was then the First Sea Lord of the British Admiralty, changed all this. He swept all the medium-sized guns away and gave this new ship TEN of the largest guns then in use.

The advent of this ship startled the whole naval world, for it was seen at once by all those able to judge that there was a vessel which might be expected to sink with ease any other ship afloat. The onslaught from those ten guns would be more than any other ship could stand. So other powers set to work to copy more or less exactly, while Great Britain quickly built more like her. So important was this new invention that very soon the strength of the naval powers began to be reckoned entirely on the number of Dreadnoughts they possessed, the older ships being left out of account as though they did not make any difference one way or the other.

But Great Britain was not content with the Dreadnought, for each succeeding ship or set of ships was improved until, only four years later, there was launched the Orion already referred to, nearly 5000 tons bigger, with 2500 more horse-power, and with 13½-inch guns instead of 12-inch. The Orion and her sisters are often spoken of as super-Dreadnoughts.

The Dreadnoughts as a class are often referred to as "all-big-gun" ships, since that is the feature which most distinguishes them from those which went before.

These large guns are mounted in turrets as they are called. We might describe these as turn-tables with a cover over something like a small gas-holder. There are usually two guns in each turret, although there are a few ships whose turrets have three in each.

The turrets seem to be standing on the deck of the ship and it is by turning them round that the guns are trained or pointed at their target.

The original Dreadnought had one turret in front and two behind, all on the centre-line of the ship, and two more, one each side, amidships. In late vessels all five turrets are on the centre-line. Thus the Dreadnought can fire six guns ahead, eight astern and eight to either side, while the newer ships can fire four ahead, four astern and all ten on either side.

There are other battleships with even more guns than these, such as the U.S.A. ship Wyoming, with twelve 12-inch guns, but the British Navy seems to prefer to stick to the original number of ten. The reason for this is that every such ship is a compromise between three alternatives.

The three great features have already been pointed out, namely, the guns, the armour and the propelling machinery. Either of these can be increased at the cost of one or both of the others, but all cannot be increased without sinking the ship, unless indeed, the ship be made larger and then other considerations crop up.

And that brings us to another class of ship often ranked among the battleships. These remarkable vessels are also termed cruisers and the fashion seems to have established itself of combining the two names and calling them battle-cruisers. They gave a fine account of themselves during the war.

The first three of these, of which the Invincible is usually taken as the type, made its appearance the year after the Dreadnought, and like the latter were the offspring of the fertile brain of Lord Fisher. The Invincible was about the same size as the Dreadnought, but had nearly twice the horse-power (41,000), which enabled it to attain an actual speed of nearly six knots more, namely, 28·6.

For guns it had eight of the same large weapons, and it was armoured with 7-inch steel armour-plates instead of 11-inch.

Thus we see illustrated what has just been said, less guns and thinner armour, to allow for more engine power and higher speed. Or, to put it the other way, we observe how higher speed was attained at the expense of the guns and the armour.

But just as the Dreadnought was followed by other still greater improvements in the same direction we get, in 1910, the famous ship Lion, a vessel not unknown to the Germans, a "super-Invincible."

This ship has a tonnage of over 26,000 and 70,000 horse-power. It was designed to do 28 knots.

We saw the use of these ships in the Jutland battle, when, using their high speed, they attacked the German battleships and kept them engaged while the slower battleships came up. Though they suffered severe losses, which probably the more heavily armoured battleships would have escaped, they held the Germans so that it was only the failing light which saved them from utter destruction.

Another example was the way in which they hunted down Von Spee and his squadron off the Falklands, when they caught the Germans because of their higher speed and then sank them by means of their heavier guns with practically no loss to themselves.

We saw them again in the Heligoland battle, coming up to the assistance of the lighter vessels just in the nick of time and scattering the enemy like so much chaff.

A fact little known to most people and productive of much surprise is that these battleships and cruisers are not such very large vessels, when compared with those of the merchant service. The Lion is 660 feet long and 86 feet wide, the Aquitania is 930 feet long and 98 feet wide, and the Olympic is 882 feet long and 92 feet wide.

The mighty Orion makes a poorer showing still in point of size, since she is only 545 feet long and 88 feet wide—little over half the length of the Aquitania.

It is difficult to compare the tonnage of a warship with that of a merchant ship, since they are not measured in the same way. The former is the "displacement" or actual weight of water displaced: in other words the precise weight of the vessel in tons of 2240 lbs.

The tonnage of a merchant ship, however, has nothing to do with weight but is based upon capacity and is arrived at by a purely arbitrary rule, thus: all the enclosed space in the ship is measured in cubic feet and the total is divided by one hundred. That gives the gross tonnage. To arrive at the net tonnage the space occupied by the engines and all other space necessary for the working of the ship is excluded. Originally the tonnage of a merchant ship was the number of "tuns" of wine which it could carry.

Thus, you see, comparing the tonnage of a warship with that of a merchant ship is somewhat like comparing a pound with a bushel. Net registered tonnage is generally considerably less than the displacement tonnage of the same ship, so that a warship is usually less than a merchant ship of the same nominal number of tons.

And now let us turn to some of the internal arrangements of these wonderful ships, more particularly to the means for working the guns.

Each turret is placed over the top of what we might call a well, running right down deep into the inside of the ship. At the bottom of this well is the magazine, where the shells are stored and also the cartridges containing the explosive which drives the shell from the gun.

Underneath the turret, forming a kind of basement to it, is a chamber called the working chamber, and up to it the shells and cartridges pass by means of lifts. For safety's sake only a small quantity of explosives is kept here at any one time, but it is from here that the guns overhead are fed. Shells and cartridges alike pass up as required by means of hoists right to the guns. Indeed, the hoists are ingeniously contrived so that in whatever position a gun may be the hoist stops exactly opposite the breech, or opening at the back of the gun through which it is loaded. Then a mechanical rammer drives the shell or cartridge into its place in the gun.

The hoists are worked by hydraulic power or electricity, and in most cases by both, arrangements being made so that either can be used at will, thus serving as alternatives in case either should get out of order.

The turrets themselves are also turned by power. Indeed, so heavy are the weights involved that only by the use of carefully designed machinery is the operation of such great weapons made possible. A single shell of the 13·5-inch gun weighs 1250 lbs.

Around each turret there is placed a wall of thick armour plate as high as it is possible to make it without interfering with the movement of the guns. This is called the barbette armour and the space enclosed by it, in which the turret stands, is called a barbette, an old fortification term meaning a place behind a rampart.

The turret is covered over, as has already been remarked, by a steel hood, so that altogether the guns and their crews are about as well protected as it is possible to be.

That all this means a considerable burden upon the ship is shown by the fact that a pair of 12-inch guns with their turret and barbette armour will weigh something like 600 tons, and if there be five of them that means 3000 tons in all.

Down below in the magazine there are lifting appliances whereby the shells can be readily picked up and run to the hoist. Moreover, there is elaborate machinery for keeping them cool. Our allies the French had, years ago, several bad accidents through the explosives going off spontaneously in their ships, and this is quite likely to happen if the magazines become too hot. So refrigerating apparatus is installed similar to that employed in meat-carrying ships, which provides a constant flow of cool air into the magazines.

The ships also are subdivided to the greatest possible extent consistent with efficient working, so that in the event of a collision or a torpedo making a hole below water the ship may not sink. As far as possible the divisions or bulkheads are made to run right from top to bottom without any openings, but that obviously is a very inconvenient arrangement, so in many places there have to be doorways through them, leading from one part of the ship to another. In such cases these are closed by water-tight doors, which can be shut before the ship goes into action or into any dangerous region.

The engines of these vessels are now always turbines. This type of engine has many advantages over the older type, in which certain parts move to and fro, that motion being changed by cranks into a round and round action. For one thing, they are lighter for a given power, so that more power can be put into a ship without adding to the weight. That means higher speed. Then there is less to get out of order. Anyone who has been into a ship's engine room where to and fro or reciprocating engines are at work will realize this, for there is a maze of rods and cranks all moving together, and many parts which need to be oiled while in motion and which would get hot and tight if they were not carefully looked after. All this in an enclosed space with possibly an uncomfortable motion of the whole ship used to make the engineer's life at sea a very hazardous and unhappy one.

But the turbine is entirely enclosed. There is nothing to be seen moving at all. Indeed, there is only one moving part, and that is coupled directly to the propeller-shaft, so that nothing could possibly be simpler.