All About Engines

296 All About Engines what is involved in the facts pressed into the fore- going paragraphs. Here is a great ship of 33,000 tons propelled through the water at a speed of 26 knots, or 30 miles, an hour. How is this done ? Steam produced in the twenty-five boilers at a pressure of 200 lb. on the square inch impinges upon hundreds of thousands of delicate blades, set in massive steel drums weighing from 60 to 126 tons. The force exerted by the steam upon a single blade is hardly measurable; but multiplied by hundreds of thou- sands it suffices to do work at the rate of 70,000 horse - power, and to carry several thousand people with speed, comfort, and safety across thousands of miles of restless sea. Was there ever a more won- derful example of man s power over the forces of Nature, or of the progress which has been made in our own day ? Again, the great 30,000-ton battle cruisers of the British Navy, cleaving the waters of the North Sea in their perpetual vigil, and capable when an enemy is sighted of springing forward at 30 knots, or nearly 35 miles, an hour, depend in the same way upon the multiplication of almost infinitesimal forces. Every modern ship of war, except the submarines, is turbine driven, and in every case we pin our faith to thousands of strips of brass, many of which, taken singly, a boy could bend across his knee. And this faith, though we are barely conscious of it, im- plies confidence not only in the dead matter of which the machinery is made, but also in the knowledge of the man who designed it, in the skill and honesty