The following process for the above purpose, is adopted in the Northern Hospital of France :The air is taken from a tower on the top of the building, so as to be always pure, and in summer cool. It is sent inside in a quantity invariably equal and of the same power, by numerous apertures in the centre of the rooms which it passes along from one end to the other, lind issues by eighteen orifices without its action being neutralized by opening one or all the windows. The steam engine is relieved in case of stoppage by another auxiliary one, and in cases of epidemic both act together to increase two-fold the supply of injected air. This engine sets in motion the ventilators for driving the air in all directions and likewise raises the water required for the hospital. The steam is likewise used for warming baths of every kind, as well as for the laundry use, the ventilation, during the whole year, consequently costs nothing. Several boilers are employed to produce the steam for the different duties of the hospital, to warm the rooms by means of hot water stoves, independent of each other, to ventilate the six wards by a steam engine, to heat the office stoves, the baths, 'c., to raise the water and wash the linen. These are placed in a court behind, away from the patients and conveniently to the kitchen. There is an open grate on the ground floor of each building, for those preparations that must be made over a fire, and the heat from the smoke is employed to ventilate the water-closets. The expense of warming the hospital in winter is $2,805, and that of ventilating it in summer $935, which is paid for by the employment of the steam for warming the baths. [Genie In- dustriel.