When the helm is normal the longest radius of the eccentric is turned towards the rack. In this position it exerts least power; but least power is then needed. As the helm goes over, the radius of the cogs gradually decreases, and its leverage proportionately increases. So that the engine is taxed uniformly all the time.
Some war vessels, including the ill-fated Russian cruiser _Variag_, have been fitted with electric steering gear, operated by a motor in which the direction of the current can be varied at the will of the helmsman.
All power gears are so arranged that, in case of a breakdown of the power, a hand-wheel can be quickly brought into play.
A railway locomotive sends the exhaust steam up the funnel with sufficient force to expel all air from the same and to create a vacuum. The only passage for the air flying to fill this empty space lies through the fire-box and tubes traversing the boiler from end to end. Were it not for the "induced draught"--the invention of George Stephenson--no locomotive would be able to draw a train at a higher speed than a few miles an hour.
On shipboard the fresh water used in the boilers is far too precious to be wasted by using it as a fire-exciter. Salt water to make good the loss would soon corrode the boilers and cause terrible explosions. Therefore the necessary draught is created by _forcing_ air through the furnaces instead of by _drawing_ it.
The stoke-hold is entirely separated from the outer air, except for the ventilators, down which air is forced by centrifugal pumps at considerable pressure. This draught serves two purposes. It lowers the temperature of the stoke-hold, which otherwise would be unbearable, and also feeds the fires with plenty of oxygen. The air forced in can escape in one way only, viz. by passing through the furnaces. When the ship is slowed down the "forced draught" is turned off, and then you see the poor stokers coming up for a breath of fresh air. In the Red Sea or other tropical latitudes these grimy but useful men have a very hard time of it. While passengers up above are grumbling at the heat, the stoker below is almost fainting, although clad in nothing but the thinnest of trousers.
In the engine-room also things at times become uncomfortably warm. Take the case of the United States monitor _Amphitrite_, which went into commission in 1895 for a trial run.