42 THE GRAPE. 



any noxious gases, and if constructed on the best plan, 

 may be placed on the credit side of expenses, there is also 

 a steady heat in the working, and a sufficiency of bulk in 

 the quantity of water, which, when once put in motion, 

 continues to flow with increased or lessened velocity, ac- 

 cording as the fire is kept up, and for some time even 

 after no further heat arises from the furnace. There have 

 been different methods adopted, as reservoirs for circula- 

 ting hot water, such as lining the inside of brick flues with 

 cement ; tanks of wood ; tin or sheet iron troughs, with 

 the tops left loose, to be covered or not, as circumstances 

 may dictate ; circular copper, tin, zinc, and cast iron 

 pipes. The cemented flue is objectionable, as the material 

 is so non-conducting, that there is great loss, and the 

 cement is also liable to crack, which causes leakage. The 

 open tank, and trough is well enough for a propagating 

 house, which is generally small, and kept very damp, but 

 is not suitable for a grapery, in which is required, a moist 

 or dry atmosphere, according to the different stages of 

 growth ; this plan also occupies much space, and looks un- 

 sightly. Tin pipes are not advisable from their tendency 

 to corrode, and unendurable qualities. Zinc softens when 

 hot, and is next to useless, copper if made strong enough 

 to resist hard knocks, and be really serviceable is very 

 expensive, so we are driven to the last substitute, cast 

 iron, which answers every purpose, is lasting, erected 

 comparatively cheap, strong, and the different lengths are 

 readily cemented, the joints becoming as firm and tight as 

 any other part. The construction of boilers for this pur- 

 pose is also various, and there is a great difference in the 

 consumption of fuel, according with the ratio of heat dis- 

 tributed to the water. In the most primitive boilers, the 

 fire only played on the under surface, and the consequence 

 was, a great waste of heat, unless the residue was con- 



