[Pg 21] In 1782, Watt patented two other features which he had invented as early as 1769. These were the double acting engine, that is, the use of steam on both sides of the piston and the use of steam expansively, that is, the shutting off of steam from the cylinder when the piston had made but a portion of its stroke, the power for the completion of the stroke being supplied by the expansive force of the steam already admitted.
He further added a throttle valve for the regulation of steam admission, invented the automatic governor and the steam indicator, a mercury steam gauge and a glass water column.
It has been the object of this brief history of the early developments in the use of steam to cover such developments only through the time of James Watt. The progress of the steam engine from this time through the stages of higher pressures, combining of cylinders, the application of steam vehicles and steamboats, the adding of third and fourth cylinders, to the invention of the turbine with its development and the accompanying development of the reciprocating engine to hold its place, is one long attribute to the inventive genius of man.
While little is said in the biographies of Watt as to the improvement of steam boilers, all the evidence indicates that Boulton and Watt introduced the first “wagon boiler”, so called because of its shape. In 1785, Watt took out a number of patents for variations in furnace construction, many of which contain the basic principles of some of the modern smoke preventing furnaces. Until the early part of the nineteenth century, the low steam pressures used caused but little attention to be given to the form of the boiler operated in connection with the engines above described. About 1800, Richard Trevithick, in England, and Oliver Evans, in America, introduced non-condensing, and for that time, high pressure steam engines. To the initiative of Evans may be attributed the general use of high pressure steam in the United States, a feature which for many years distinguished American from European practice. The demand for light weight and economy of space following the beginning of steam navigation and the invention of the locomotive required boilers designed and constructed to withstand heavier pressures and forced the adoption of the cylindrical form of boiler. There are in use to-day many examples of every step in the development of steam boilers from the first plain cylindrical boiler to the most modern type of multi-tubular locomotive boiler, which stands as the highest type of fire-tube boiler construction.
The early attempts to utilize water-tube boilers were few. A brief history of the development of the boilers, in which this principle was employed, is given in the following chapter. From this history it will be clearly indicated that the first commercially successful utilization of water tubes in a steam generator is properly attributed to George H. Babcock and Stephen Wilcox.
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Woolworth Building, New York City, Operating 2454 Horse Power of Babcock & Wilcox Boilers