WARMING AND VENTILATING OCCUPIED BUILDINGS. 



4 cubic feet an hour, are usually enough. The heat given out by the 

 combustion of gas produces in the flue an increase of temperature, 

 which keeps up the draught of the stoves or chimney. After the fire is 

 well started, the gas-jets may be put out. An arrangement of this kind 

 applied at the conservatory to a stove, the draught of which could not 

 be kept up regularly by an extra fire of the usual kind, and which was 

 also in very bad condition, succeeded very well, even during strong 

 winds. 



STEAM-HEATING. 



24. The rapid circulation of steam even under very slight pressure, 

 and the large amount of heat it gives out in condensing, are the princi- 

 pal advantages of this mode of heating, which only requires, for the 

 passage of the steam, pipes of small dimensions, but it has with the 

 forms of apparatus most in use very grave defects. 



Irregularities in the fire affect very sensibly the circulation of steam, 

 and want of attention, especially apt to occur during the night, leads to 

 condensation. When the fire becomes hot again, the steam, which then 

 flows quickly into the pipes, where a partial vacuum has formed, meeting , 

 a great deal of condensed water, drives it violently, and the shocks 

 occasionally produce explosions, often cracks and leaks, or at least very 

 frequent disagreeable noises. 



These great objections have generally led to the abandonment of 

 warming by direct steam -circulation, except in factories where the 

 escape-steam from the engines is made use of. In that case it flows 

 constantly through large exposed pipes, having a slope sufficient to pre- 

 vent the accumulation of condensed water. But when it is designed to 

 warm dwellings by carrying the steam through thin floors, the difficul- 

 ties increase, and all the unpleasant effects become manifest. 



Grouvelle, a skillful civil engineer, has designed and constructed for 

 several hospitals an arrangement in which the steam does not directly 

 heat the radiators placed in the rooms, but the steam-pipes heat water 

 placed in those radiators. This system, in consequence of the great 

 density of water and its imperfect conductibility of heat, prevents the 

 too sudden checking of the radiation when the flow of steam is dimin- 

 ished or stopped. These radiators have, on top, a little opening, which 

 prevents the temperature of the water from rising above 212°, and the 

 l)ipes which furnish a i^assage for the air coming in from the outside 

 do not allow the temperature of that air to exceed 104° or 113°. 



Special arrangements also allow the steam to be carried through the 

 radiators, or through external pipes, so as to moderate the temperature 

 of the room by using only a few of the radiators. But if this plan 

 secures a more regular warmth, it does not prevent trouble from con- 

 densation in the pipes passing through the floors, nor from leaks, which 

 are always difficult to discover and to stop. Some accidents which have 



