238 on rendle's tank system of heating by hot water. 



and fits exactly within the top of the boiler. This answers the double 

 purpose of containing a body of fuel, which settles down and supplies 

 the fire during the night ; and, when the lid is placed upon the outer 

 case, of checking the draught of the fire, which is only continued 

 through some small passages cut in the sides of the cylinder. A 

 small opening also communicates with the fire from the outside, 

 through which the former can be stirred when necessary. 



During the time in which this system has been in working, the 

 water has never been within many degrees of the boiling temperature, 

 yet the thermometer within the house has seldom, on the coldest 

 nights, fallen below 60° or 65°. Its great advantages are, that the 

 tank in which the water circulates will, with such modifications as 

 circumstances may require, serve as a stage for plants, either in the 

 centre or round the sides of a house, by which the expense of hot- 

 water pipes will be dispensed with ; and its extreme simplicity, 

 which is such that any person situated at a distance from engineers 

 might, with a little ingenuity and the assistance of a carpenter and 

 blacksmith, erect an apparatus of his own, since any boiler which 

 would create a circulation of water would answer as well as the one 

 above described, although it might not be equally economical. We 

 may also state that the atmosphere of the house in which this system 

 is adopted is remarkably pure. 



Mr. Rendle observes, it is a plan which can scarcely be recom- 

 mended too strongly ; for, not only is it adapted for the smallest 

 propagating-house, but also for plant structures of the largest size. 

 My tank or cistern is about 20 feet long and 5 feet broad ; it is situ- 

 ated in the centre of a house, and, except at the end where the boiler 

 is fixed, is surrounded by a walk. The boiler is one of Rogers's, 

 and acts admirably. The depth of the tank is only six inches, 

 and this is quite sufficient. On the top I have placed large slate 

 slabs, cemented to each other, to prevent a superfluity of steam from 

 escaping into the house. (Tiles, it is stated, being more porous, are 

 better.) 



When first I thought of this excellent mode, I imagined that, to 

 keep up a sufficient heat in the house, I should be obliged to retain a 

 constant fire ; but such is not the case. If the fire is lighted for two 

 hours in the morning and evening, it is quite sufficient to maintain a 

 steady and genial bottom heat ; as the large body of water in the 



