378 S. Webber on Ventilation. 
their excess of caloric;:and sink like their predecessors, while 
any portion that passed outwardly to the ground would be re- 
placed by a portion of the cooler external air that would press in 
to supply the vacuum ; and this, receiving heat from the warmer 
carbonic acid in the room, would become more rare than the 
warm carbonic acid itself, and still more so than that which it 
had deprived of a portion of its caloric, and would rise rapidly to. 
the top displacing and forcing downwards and outwards an 
equivalent bulk of the carbonic. Thus currents. inwards and 
outwards would soon be established, which would soon reduce 
the whole carbonic acid to the temperature of the external air, 
and the level of it, to the bottom of the window. 
When this takes place the regular action of the currents is very 
greatly checked, the’carbonie acid below that level is cooled down 
to the temperature of the external air, and from its greater specific 
gravity is disposed to rest like a fluid within its lateral confining 
walls, with a level and even surface. But as water when so con- 
mospheric, the actions would all be inverted, but the result would 
be the same—the complete disa 
the substitution of pure atmospheric air in its place. 
uppose that into a close and cold room a permanent source of 
pure calorie be introduced ; the air immediately around it becom- 
ing heated will rise rapidly to the ceiling, and there diffuse itself, 
becoming cooler as it spreads along the ceiling, by imparting part 
of its caloric to that. ‘The air around that which became heated 
and rose, will rush in and up, to take its place, become heated 1n 
its turn and rise, be diffused along the ceiling pressing forwal 
that which rose before it. This will go on till all the cold air im 
the room has in its turn been heated and risen up to the ceiling; 
been diffused along it and forced down by its ated presst 
and the obstacle of the sides‘of the room. Then that poruiom 
“ite 
