Below it is shown the Water Turbine, the principle of which is evident from the sketch.
From each of the apertures a stream of water is forcibly directed, and, by its resistance, spins the vessel round and round. There are several shops in London in which this instrument may be seen at work.
Although in such positions it is necessarily a mere toy, it carries with it, in common with many other toys, the germs of valuable inventions. Indeed, there have been attempts to utilise the principle of Direct Action in the propulsion of vessels, but as yet the mechanical difficulties have proved practically insuperable, and, although a vessel has been thus propelled, the expense has been heavier than that of the paddle or screw, and the speed not nearly so great.
On the right hand of the illustration is another example of Direct Action, called the Electric Tourniquet.
In the two previously mentioned instruments the motive power is visible, but in this it is invisible except in the dark.
The principle is exactly the same as in the pocket or water tourniquet; but, instead of heated air or a stream of water, electricity is used. The instrument is attached to an electric machine, and fully charged. The electric fluid rushes out of the points, forces itself against the air, and so, by its recoil, drives the machine round and round upon its pivot.
We will now take two examples of Direct Action as found in Nature.
Perhaps many of my readers have seen the Octopus, and admired the manner in which it glides through the water, trailing its long arms behind it. Whence the force comes is not easily seen, and the creature appears to move almost by volition. In reality, however, it employs Direct Action. It takes water into the body, and then it ejects it through a tube called the “siphon” with such force that the animal is propelled backwards through the water.
Some of the creatures belonging to the Cuttles, and popularly called Squids, can use such extraordinary powers that they can project themselves far out of the water. In consequence of this power, they are sometimes called Flying Squids, and, as they have been known to shoot themselves completely over the hull of a large ship, they well deserve the name.
The common Squid of our coasts, which furnishes the so-called Cuttle-bone, affords us a good example of Direct Action. I once hatched a number of young Squids from the grape-like eggs, and it was most curious to see how the little creatures shot about as soon as they escaped from the egg.