1869.] Descriptions. 509 by the gas-lights, and the flues from the space immediately under the floors — which it is also proposed to have a little warmer, than the average temperature of the room — are all carried directly upwards ; and enter the main shaft near the top. It is proposed to have a coil of steam- pipes, in the horizontal air duct, over the fourth story. Although this is heating the ventilat- ing flues at the top, which was so strongly condemned above ; yet, in this instance — as it is placed so far from the main shaft, and these flues are in the centre of the building, and mostly warmer than the rooms — it is believed, that it will be easier for the vacuum, created by the heat, to be supplied by the air flowing up these flues, than in any other way. In that case, there would be no l'eturn current. The supply of the fresh air to this building, was a matter of much solici- tude, as, from the immense amount of bituminous coal burned in Pittsburgh, indicated by the dense clouds of smoke, belching forth from its forests of factory chimneys, the whole air is filled with soot. If a window is raised, to let in the fresh air, in a few moments every thing in the room is covered with particles of soot, some small and some not small. It is, therefore, proposed to use a large room in the cellar, thirty-six feet square and twelve feet deep, for a set- tling-chamber ; and allow all the air, for the whole building, to enter that way, through fine wire screens, which will catch some of the largest particles of soot floating in the air. These screens will be so arranged, that they can be swept down, or cleaned, every morning; and probably, brushed over with oil, to assist in catching the particles of soot. In cold weather most of the fresh air, that is required for ventilation, through- out the building, will be slightly warmed by passing over steam-pipes in the cellar. It is not designed to heat this fresh air, but merely to warm it to 50° or 55°, to prevent its forming unpleasant cold currents, as it enters the rooms, and avoid too great a shock to the lungs. The additional warmth required will be sup- plied by direct radiation, from the steam radiators shown under the windows, and the slightly augmented heat proposed to be given to the floor by the steam- pipes under them. This proposition of warming the floors — so as to keep the feet warm, and allow the head to be surrounded by cool, fresh, invigorating air for breathing — is be- lieved to be of much importance. It is so contrary, however, to the pre- vailing custom, which is to keep the head in an atmosphere of from 70° to 80°, while the feet are from 50° to 60°, that it may take some time to become accustomed to it, and ascertain the most desirable temperature to keep the floor at, which is probably that of 10° below the temperature of the body — say 88° or 90° — which would feel cool to the touch, and perhaps, be found most agreeable. It will thus be seen, that great care has been taken, to study the natural movements of the air in the building, and to work with these currents, and never to oppose them, in any important particular. All excessive draughts have been care- fully avoided ; yet, while it may be al- most impossible to discover any per- ceptible currents of air, in any of the rooms, in passing through them, yet it will be also almost impossible to find any stagnation of the air in any parts. The heating surface is so distributed, throughout the edifice, with the excess 1 of heat to meet the excess of cold, that, if all the doors are thrown open, over the whole building, there will be an even, uniform temperature throughout. Or, if the doors should be all shut, with fire in the ventilating stacks, the con- stant motion of the air will be equally well secured in that way.
