198 THE POPULAR SCIENCE MONTHLY. 



The most recent improvements in the use of the German stove for 

 warming have been introduced by Dr. Bohm, in the Rudolf Hospital 

 at Vienna. He there warms fresh air by means of passages con- 

 structed in the fire-clay stoves, placed in the ward, and the fresh 

 warmed air passes into the ward from the top of the stove. He pro- 

 vides flues of a large size, and proportioned to the size of the ward, 

 from the level of the ward floor to above the roof, and the difference 

 of temperature between the air in the ward and the outer air causes a 

 sufficient current in these flues to ventilate adequately the ward. By 

 this means the fresh warmed air, instead of passing off to the upper 

 part of the ward and then away by flues there, is made to circulate 

 toward the floor of the ward, thus bringing into action the principle 

 by which the open fireplace is useful in ventilation. But this arrange- 

 ment destroys one element of economy in the German stove, because 

 the heat generated, instead of being left to pass slowly off into an un- 

 ventilated room, is removed rapidly by the fresh air passed into the 

 ward, and has, therefore, to be renewed at intervals, instead of, ac- 

 cording to usual custom, the stove being left shut irp for twenty-four 

 hours to give off its heat slowly. The larger the supply of warmed 

 air, the larger must be the consumption of fuel ; and, if the heat is to 

 be supplied economically, it must be through a good conducting me- 

 dium ; but the material of the German stove is a bad conductor of 

 heat. 



The old Roman system of warming by means of a fire under the 

 floor produced a most agreeable and equable temperature, but it did 

 not assist the ventilation, and' it was not economical, in that the floor, 

 being of tiles, was of a bad conducting material, and much of the heat 

 was absorbed in the ground or surrounding flues. According to Pliny, 

 the smoke was carried to the wood-house to be used in drying the 

 wood for burning. I recently made an experiment to compare the 

 effect of warming by means of a heated floor with the heating effect 

 of a ventilating fireplace ; the experiment lasted, with each mode of 

 warming, for two days. It showed that, in the case of the warmed 

 floors, the room was maintained at a temperature of about 18 above 

 the temperature of the outer air with an expenditure of 56 lbs. of coal 

 and 112 lbs. of coke, while with the ventilating fireplace the expendi- 

 ture was only 75 lbs. of coal; the cost being 35. Ad. for the warmed 

 floor as compared with Is. Ad. for the ventilating fireplace. 



A more complete plan of warming a building is by means of a fire 

 from which the heat is conveyed, either by hot-water pipes or hot air, 

 to the various parts of the building. 



Warming by means of air conveyed by flues to various parts of 

 the building, will answer, as a rule, in ordinary existing houses, best in 

 connection with open fireplaces, which draw in the warmed air to the 

 various rooms, because there must be some means of forcing or draw- 

 ing the warmed air into the house, and it would not be convenient to 



