The next year we were not exhibitors at the Institute fair, but our boiler remained in its place and was run by the Institute. This boiler and its setting are shown correctly in the accompanying reproduction of a drawing made about that time, except that it consisted of nine sections instead of six. At the close of the exhibition a boiler test was made by the Institute, through a committee of which Professor Thurston, at that time Professor of Mechanical Engineering in the Stevens Institute, afterwards until his death Director of the Sibley College of Mechanic Arts, in Cornell University, was the chairman. Five boilers, including the Allen boiler, were tested, one on each day, in a continuous run of twelve hours. The four besides our own were all different from the boilers exhibited the year before. A week was spent in preparation for this test. A large wooden tank was constructed, in which was built a surface condenser, consisting of a pile of sections of the Root boiler, laid horizontally, having a total of 1100 square feet of cooling surface. The steam was exhausted into the pipes which were surrounded by the cooling water, thus reversing the construction of surface condensers. [Illustration: Professor ROBERT H. THURSTON] [Illustration: ALLEN BOILER. OF 80 HORSE POWERS. _Area of Effective Heating Surface 810-Square Feet._ _ „ „ Grate „ 24 „ „_ _scale-1 inch-1 foot._ _Allen Engine Works._ _July-1872._] Each boiler was tested by setting its damper and its steam-valve wide open, so burning all the coal that could be burned by it under its draft, and delivering freely all the steam that it made. This latter entered the condenser at the top, and the water formed by condensation was drawn off at the bottom, while the condensing water entered the tank at the bottom and was drawn off at the top, the currents of steam and water being thus opposite to each other, which was an ideal construction. The condensing water at a temperature of 45.5 degrees flowed in under the pressure in the city main and was measured in a Worthington meter, and the temperature of the overflow taken. The condensed steam was drawn off into a barrel and weighed, 300 pounds at a time, and its temperature taken. This method was an excellent one. Not having high chimneys, no boiler had a strong draft, as shown by the coal burned per square foot of grate. Our draft was the strongest of all. Only the Allen boiler and the Root boiler gave superheated steam, and the competition between them was very close. The valve being wide open, giving a free current into the condenser, the superheat of our steam fell to 13.23 degrees Fahrenheit. Root’s superheat was 16.08 degrees.