the sensible state, will again raise the temperature of pipes.
But as soon as they are a second time cooled down below 212 deg. a further
portion of steam will condense, and a further quantity of latent heat
will pass into the state of heat of temperature, and so on until the
whole quantity of latent heat has been abstracted and the whole of the
steam condensed, in which state it will possess just as much heating
power as a similar bulk of water at the like temperature; that is, the
same as a quantity of water occupying 1-1694th part of the space that
the steam originally did.

By experiments made by the above authority, it has been proved that a
given bulk of steam will lose as much of its heat in one minute as the
same bulk of hot water would in three hours and three quarters. And
further admitting that the heat of cast iron is nearly the same as that
of water, if two pipes of the the same calibre and thickness be filled,
the one with water and the other with steam each at 212 deg. of temperature,
the former will contain 4.68 times as much heat as the latter;
therefore if the steam pipe cools down to 60 deg. in one hour, the water
pipe will take four hours and a half to cool down to the same point. In
a hot water apparatus we have in addition to the above, the heat from
the water in the boiler, and of the heated material in and about the
furnace, which continues to give out heat for a long time after the fire
is totally extinguished; whereas in a steam apparatus, under the same
circumstances we have no source of heat except the pipes by which it is
conveyed--giving an advantage in favor of hot water over steam as
regards its power of heating hot houses, and maintaining heat after the
fire ceased to burn, in nearly the proportion of 1 to 7--that is, hot
water will circulate from six to eight times longer than steam under the
above circumstances."

TANKS.--This mode of heating horticultural buildings has been used in
England for some years, and has, of late, obtained considerable
popularity in this country; mainly, however, for the purpose of
obtaining bottom heat. The tank method is more steady and reliable in
its operations in this respect, than heating by flues or pipes, but even
its most strenuous advocates must admit that for atmospheric heat hot
water pipes or flues must be employed in some shape or other, where the
tanks are covered with earth or sand beds for propagating purposes.
With slate or metallic coverin