“One minute and thirty-two seconds,” said one.

“Right,” answered the others.

Then, as the wonderful yacht Arrow gradually slowed down, they tried to realise the speed and to accustom themselves to the fact that they had made the fastest mile on record on water.

And so the Arrow, moving at the rate of forty-six miles an hour, followed the course of her ancestress, the Clermont, when she made her first long trip almost a hundred years before.

The Clermont was the first practical steamboat, and the Arrow the fastest, and so both were record-breakers.  While there are not many points of resemblance between the first and the fastest boat, one is clearly the outgrowth of the other, but so vastly improved is the modern craft that it is hard to even trace its ancestry.  The little Arrow is a screw-driven vessel, and her reciprocating engines—­that is, engines operated by the pulling and pushing power of the steam-driven pistons in cylinders—­developed the power of 4,000 horses, equal to 32,000 men, when making her record-breaking run.  All this enormous power was used to produce speed, there being practically no room left in the little 130-foot hull for anything but engines and boilers.

There is little difference, except in detail, between the Arrow’s machinery and an ordinary propeller tugboat.  Her hull is very light for its strength, and it was so built as to slip easily through the water.  She has twin engines, each operating its own shaft and propeller.  These are quadruple expansion.  The steam, instead of being allowed to escape after doing its work in the first cylinder, is turned into a larger one and then successively into two more, so that all of its expansive power is used.  After passing through the four cylinders, the steam is condensed into water again by turning it into pipes around which circulates the cool water in which the vessel floats.  The steam thus condensed to water is heated and pumped into the boiler, to be turned into steam, so the water has to do its work many times.  All this saves weight and, therefore, power, for the lighter a vessel is the more easily she can be driven.  The boilers save weight also by producing steam at the enormous pressure of 400 pounds to the square inch.  Steadily maintained pressure means power; the greater the pressure the more the power.  It was the inventive skill of Charles D. Mosher, who has built many fast yachts, that enabled him to build engines and boilers of great power in proportion to their weight.  It was the ability of the inventor to build boilers and engines of 4,000 horse-power compact and light enough to be carried in a vessel 130 feet long, of 12 feet 6 inches breadth, and 3 feet 6 inches depth, that made it possible for the Arrow to go a mile in one minute and thirty-two seconds.  The speed of the wonderful little American boat, however, was not the result of any new invention, but was due to the perfection of old methods.