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Transactions of the Horticultural Society. 



two directly above these, and just below the surface of the 

 water. The house is divided by glazed partitions into three 

 compartments (d ef), for the convenience of forcing one part 



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ft 



without the other. The middle compartment is two lights in 

 width, and the other two have four lights each. The pipes 

 from the boiler go horizontally to the front of the house, where 

 one upper and one lower pipe branch to the east compartment, 

 and other two pipes to the west, and are carried to the ends 

 of the house along the sides of the flues, where they unite to 

 cast-iron reservoirs at each end of the house (g g) ; which re- 

 servoirs are each three feet six inches long, one foot six inches 

 wide, and one foot eight inches deep, having iron covers. 

 These reservoirs are filled with water, that communicates, by 

 means of the pipes, with the water in the boiler. 



" When the boiler, pipes, and reservoirs are filled, and a fire 

 lighted under the boiler, the heated water, ascending to the 

 top of the boiler, forces its way along the upper pipes to the 

 reservoirs, the cold water finding its way back to the bottom 

 of the boiler through the under pipes ; and the circulation con- 

 tinues regular as long as there is any heat under the boiler, the 

 hot water flowing through the upper pipes to the reservoir, and, 

 as it cools, returning back to the boiler through the under pipes. 

 I have repeatedly, after the water has been heated, immersed 

 a thermometer in the reservoirs at the ends of the house, and 

 have only found a difference of three or four degrees between 

 that and the water in the boiler. It is not necessary to make 

 the water boil ; and, if the fire is judiciously managed, no steam 

 will be raised, and no water wasted. It is, however, necessary 

 to examine the boiler occasionally, and to add water when 

 any has evaporated. 



