One feature of the Fair of 1885 that attracted much attention and comment, was the novel and unique display of mechanical models designed and constructed by the boys of the third grade in Grammar-School, No. 57, one of the public schools of New York City. The work exhibited by these boys is peculiarly interesting and suggestive, and is an indication of what observant, thoughtful, and intelligent boys can devise and do when their tastes and natural inclinations are developed. The boys' models were made at home, after class-hours, and on odd holidays during the six months previous to exhibition, and were primarily intended to illustrate the principles of the six mechanical powers,--the inclined plane, the lever, the wedge, the pulley, the wheel and axle, and the screw. When the American Institute Fair opened, an inclined railway, with its platform and cars; a miniature guillotine, with ready knife; a dumb-waiter in full working order; a derrick prepared to raise many weights; a pile-driver with its automatically dropped weight, the sound of which never failed to attract attention,--all these, with other models, occupied a space in Machinery Hall. During the morning hours, curtains screened the models; in the afternoon the youthful exhibitors arrived and took special delight in showing the working of their designs. The pleasant hours spent there, the praise of visitors, and the recognition and commendation accorded by the press will be long remembered by the boys. At the closing of the Fair, the exhibit was awarded the Medal of Merit. The illustrations on pages 548 and 550 show the models exhibited. Figure 1 represents an alcoholic furnace, illustrating the expansion of a brass rod by heat. A cylinder of tin, fifteen inches in height and five in diameter, is hinged to a base of wood and arranged so as to tilt to the left. A lever fifteen inches long opens and closes a damper; this lever (an umbrella rod) is inserted in a pivoted rod of wood two inches long, supported in a square frame made of an inch strip of tin bent twice at right angles and soldered to the cylinder. A brass banner rod, seven inches long, also connects with this rod and, passing through an inch opening, is supported in the flame of an alcohol lamp and fastened on the opposite side by a tiny brass knob screwed on the protruding thread of the rod. A small pulley and weight steadies the motion of the lever. The heat of the alcohol flame causes the brass rod to lengthen, and this in turn moves the lever which opens the damper; and the degree of expansion is indicated on a paper scale by a straw pointer attached to the rod of the damper. A coating of copper bronze was given to the cylinder. This model was made in part by Winfred C. Rhoades.