Page:Collier's New Encyclopedia v. 09.djvu/89

LEFT STEAM 63 STEAMBOAT Under ordinary atmospheric pressure, water boils in an open vessel at a tem- perature of 212°, and the steam always has this temperature, no matter how fast or on a screw. The term especially be- longs to steam river craft; ocean-going craft being called steamers, steamships, etc. The first steamboat was built MODERN STEAMSHIP the water is made to boil. The heat which is supplied simply suffices to do the work of converting the liquid water at 212° into gaseous steam at 212°, with- out raising the temperature of the steam at all. If the temperature of steam at 212° is lowered by only a very small amount, part of the steam is condensed; hence steam at this temperature is termed moist or saturated steam. At high tem- peratures and pressures, steam behaves like a perfect gas; but at lower pres- sures and at temperatures near the boil- ing point of water, its behavior differs markedly from that of perfect gases; and this change of properties has to be taken into account in all calculations connected with the expansion of steam in steam engines. The terms high pres- sure and low pressure are applied to steam without any sharply defined limit between them. If the steam is super- heated by passing it through hot pipes, it is converted into dry steam, which, v/ithin certain limits, behaves like a per- fect gas. If, instead of allowing the steam to escape freely, the water is boiled in a closed vessel, the steam accumulates, and both pressure and temperature rap- idly increase, till the former becomes several times greater than that of the atmosphere. If now the steam is allowed to escape, it rapidly expands, and if it escapes into the cylinder of a steam en- gine the expansion can be utilized and converted into work. As the steam ex- pands, its pressure of course becomes less and less till it is not greater than that of the atmosphere; and at the same time its temperature is reduced, the re- duction depending on the rapidity with which expansion takes place. STEAMBOAT, a boat or vessel pro- pelled by steam acting either on paddles by Denis Papin, who navigated it safely down the Fulda as long ago as 1707. Unfortunately this pioneer craft was de- stroyed by jealous sailors, and even the very memory of it was lost for three- quarters of a century. In 1775 Perrier, another Frenchman, built an experi- mental steam vessel at Paris. Eight years later, in 1783, Jouffroy took up the idea that had been evolved by Papin and Perrier and built a steamboat which did good service for some time on the Saone. The first American to attempt to apply steam to navigation was John Fitch, a Connecticut mechanic, who made his in- STEAMBOAT OF 1736 itial experiments in the year 1785. To what extent Fitch was indebted to the three illustrious French inventors named above we are not informed, but that his models were original there is not the least doubt. In the first he employed a large pipe kettle for generating the steam, the motive power being side pad- dles working after the fashion of oars on a common rowboat. In the second Fitch craft the same mode of propulsion was adopted with the exception that the paddles were made to imitate a revolving wheel and were fixed to the stern — clearly foreshadowing the present stern- wheeler.