THE BOILER-ROOM OF MACHINERY HALL.—Never before was such a boiler-room as that which delighted engineers in Machinery Hall. It must needs be enormous, for it supplied the force for all the lights and machinery of the great buildings, but those who had never seen it were none the less astonished when they entered the great room. It extended north and south in the annex, and to look down it was like looking down a street the end of which was lost in the distance. It was the largest boiler-room in the world. Not one class of boilers alone were used, but those of different manufacturers were set up side by .side and so, throughout the Fair’s continuance, they were subjected to a practical test of quality and endurance. The same rule was followed with the pumps, the boiler-room thus becoming one of the greatest competitive fields of the Exposition. It was a model boiler-room in management, too. Only petroleum was used as fuel; convenience and neatness being thus assured, and tyros had little place among the engineers in charge of a plant so expensive and working under such conditions. An amazing force emanated from that boiler-room. Underground tunnels in which pipes were laid carried steam to distant buildings where engines were in operation, and great conduits containing electric wires radiated in all directions. It was a sight worth looking at for the engineer, or the student of progress of any sort in the mechanical field, and will afford a mental object of comparison for a long time to come. It was one of the wonders of the Fair, but was recognized as such by only a portion of the visitors.