146 CULTIVATION OP THE GRAPE UNDER GLASS. 



Those who wish to experiment in this direction, and spend 

 considerable money in making these experiments, will find ample 

 opportunity for doing so ; the wise man will be satisfied " to 

 let well enough alone." 



The best method of heating all horticultural structures is by 

 hot water. Common air always contains in suspension minute 

 particles of animal and vegetable matter, besides being more or 

 less filled with aqueous vapor. When this atmosphere is made 

 to pass over highly heated metallic surfaces these particles of or- 

 ganic matter are decomposed by the heat, and resolved into their 

 various elementary gases ; and the suspended aqueous vapor is 

 also decomposed, the oxygen thereof uniting with the hot iron 

 surface, and the hydrogen mixing with the air. These changes 

 make the atmosphere extremely deleterious to both animal and 

 vegetable life. Metallic surfaces should never be heated above 

 212 degrees of Fahrenheit for all purposes of warming dwellings 

 or horticultural buildings, and where the heating is done by hot 

 water the most careless manager can never exceed this point.' 

 Heating by means of brick flues is not as objectionable as by hot 

 air stoves or furnaces; yet in our extremely cold climate, rendering 

 it sometimes necessary to heat the flues to a high temperature, 

 the organic matter in the atmosphere becomes decomposed, and 

 the expansion of bricks admits of an escape of gases from the 

 fuel, through the fissures and joints. 



Besides these reasons, a greater permanency of temperature 

 is obtained by the use of hot water than is possible by any other 

 method. Steam circulating in pipes will not maintain the same 

 permanency of temperature. A tube filled with water at a tem- 

 perature of 212° Fahrenheit contains 1694 times as much matter 

 as one of the same size filled with steam. Hence it is that a 

 given bvlk of water, in falling from a temperature of 212" to 60°, 

 wiU give out 228 times as much heat as the same bulk of steam 

 reduced to the same temperature of 60°; or, in other words, a 

 given bulk of steam will lose as much of its heat in one minute as 

 the same bulk of water will lose in three hours and three quarters. 



