One strange result of all this hammering in of rivets is that every ship by the time it leaves the slip has become a huge magnet, with somewhat disconcerting effects upon its own compasses, but of that more later on.
Thus the great ship grows, being made piece by piece in the workshops to the shapes indicated from the mould loft and put together and riveted on the slip, until finally in due time it is ready to take its first journey.
The launching of a big ship always strikes me as about the boldest and most daring thing which is ever done in the course of industry. For the huge structure, naturally top-heavy, weighing hundreds or thousands of tons, is just allowed to slide at its own sweet will. From the moment it starts until it is well in the water it is in charge of itself, so to speak, and if anything were to go wrong no power on earth could stop it once it had got a start.
That nothing ever does go wrong, or scarcely ever at all events, is due to the care with which all preparations are made before that critical moment when the ship is let loose and to the skill and experience of those in charge.
As the hull reaches that degree of completion when it can safely be put in the water, strong wooden structures termed launching ways are constructed one on each side of her. These really act like huge rails upon which in due course there will slide a gigantic toboggan. Tremendously solid and strong they have to be, as they have each to carry half the total weight of the ship.
Under each side of the ship and upon the launching ways there is built a timber framework capable of raising the ship bodily off the blocks upon which until now it has reposed. These two frames, being connected together by chains passing beneath the keel, constitute what is called the cradle, the "toboggan" which is to slide down the ways, bearing the ship upon it.
It is easy to see that being top-heavy something must be done to give the ship support before the shores on either side can be taken away, and it is equally clear that these latter must be removed before she can slide down to the water. Neither would it do to let the vessel slide upon her own plates, so we see that the cradle fulfils a twofold purpose, first enabling the ship to reach the water without ripping holes in her own plates, and secondly giving it the necessary side support to prevent it from toppling over on the way.
When all is ready, but a short time before the hour appointed for the launch, a curious operation is performed. Between the main part of the cradle and the part which actually slides upon the ways wedges are inserted, hundreds of them, and they are all driven in simultaneously. Their purpose is to make the cradle slightly higher and so to lift the ship off the blocks upon which it was built. If they were driven in one at a time each would only dig its way into the timber and nothing else would happen, but being driven all together a most powerful lifting action is produced which actually raises the mighty ship. So hundreds of men stand, each with his
hammer ready to strike a wedge, while the foreman stands by with a gong. At a stroke on the gong the hundreds of hammers strike as one, and so the ship is raised off the blocks, which can then be removed, to facilitate which they too are built of wedge-shaped pieces which can easily be knocked apart. The shores, too, have ceased to serve any useful purpose and can be taken away until at last all shores and all blocks are gone and the vessel rests upon the cradle only. Meanwhile tons of grease have been put on the ways, and the ship, urged by its own weight, is straining to get down the greasy slope into the element for which all along it has been intended. At this stage the only thing which restrains it is a kind of trigger arrangement on either side which locks the cradle in its place. In some yards elaborate mechanical catches controlled by electricity are used for this, but in many the old device of "dog shores" is still used. These are simply two stout wood props which fit between a projection on the ways and one on the cradle, there being one dog shore on either side. Just over each dog shore there hangs a weight.