To stop the Turbina was an easy matter; Mr. Parsons had only to turn off the steam.  But to make the vessel go backward another set of turbines was necessary, built to run the other way, and working on the same shaft.  To reverse the direction, the steam was shut off the engines which revolved from right to left and turned on those designed to run backward, or from left to right.  One set of the turbines revolved the propellers so that they pushed, and the other set, turning them the other way, pulled the vessel backward—­one set revolving in a vacuum and doing no work, while the other supplied the power.

The Parsons turbine-engines have been used to propel torpedo-boats, fast yachts, and vessels built to carry passengers across the English Channel, and recently it has been reported that two new transatlantic Cunarders are to be equipped with them.

[Illustration:  THE ENGINES OF THE ARROW]

A few years after the Pilgrims sailed for the land of freedom in the tiny Mayflower a man named Branca built a steam-turbine that worked in a crude way on the same principle as Parsons’s modern giant.  The pictures of this first steam-turbine show the head and shoulders of a bronze man set over the flaming brands of a wood fire; his metallic lungs are evidently filled with water, for a jet of steam spurts from his mouth and blows against the paddles of a horizontal turbine wheel, which, revolving, sets in motion some crude machinery.

There is nothing picturesque about the steel-tube lungs of the boilers used by Parsons in the Turbina and the later boats built by him, and plain steel or copper pipes convey the steam to the whirling blades of the enclosed turbine wheels, but enormous power has been generated and marvellous speed gained.  In the modern turbine a glowing coal fire, kept intensely hot by an artificial draft, has taken the place of the blazing sticks; the coils of steel tubes carrying the boiling water surrounded by flame replace the bronze-figure boiler, and the whirling, tightly jacketed turbine wheels, that use every ounce of pressure and save all the steam, to be condensed to water and used over again, have grown out of the crude machine invented by Branca.

As the engines of the Arrow are but perfected copies of the engine that drove the Clermont, so the power of the Turbina is derived from steam-motors that work on the same principle as the engine built by Branca in 1629, and his steam-turbine following the same old, old, ages old idea of the moss-covered, splashing, tireless water-wheel.

THE LIFE-SAVERS AND THEIR APPARATUS

Forming the outside boundary of Great South Bay, Long Island, a long row of sand-dunes faces the ocean.  In summer groups of laughing bathers splash in the gentle surf at the foot of the low sand-hills, while the sun shines benignly over all.  The irregular points of vessels’ sails notch the horizon as they are swept along by the gentle summer breezes.  Old Ocean is in a playful mood, and even children sport in his waters.