heated by hot Water. 

 61 



287 



0, The reservoir of the main circulation. 



b. Delivering pipe of the branch circulation, If in. in diameter. 



c. The dip into returning pipe. d. Returning pipe, entering reservoir at bottom. 

 e. Branches of f in. pipe from delivering pipe, dipping into returning one. 



/, Stopcock, to prevent the circulation, if necessary. 



g. Air-pipe; not necessary, unless the bed were large. (VoL IV. p. 18.) 



1, Delivering pipe of main circulation. 



I had previously tried to heat the hot-bed by a branch 

 from the reservoir, of equal-sized piping (see Chabannes's 

 apparatus in Vol. IV. p. 29. fig. 30.) ; but, after many fruitless 

 attempts, I found it impossible to get the water to circulate, 

 notwithstanding I bored the pipes in several places, and in- 

 serted tubes, as described by Mr. Cottam (Vol. IV. p. 18.), 

 which nevertheless evidently assisted in extending the heat. 

 Had the main circulation been constructed on the principle 

 of pressure, no doubt it would have answered. I was there- 

 fore compelled to alter the plan, according to that above, 

 which was attended with the most perfect success. Having 

 thus realised bottom heat, my next object was to attain the 

 required moisture. I accordingly extended the pipe which 

 conveys water into the house for the plants at the back of the 

 bed {Jig. 52. h), and soldered into it small shoulders with 

 stopcocks (i). To these are affixed copper tubes (/•), about 

 three eighths of an inch in diameter, which being punctured 

 laterally, I can flood the bed at pleasure, and afford it more 

 or less moisture as may be required. The tubes, which re- 

 move off and on, lie embedded on the surface of the sand. 

 The pots stand upon them as on any other portion of the 



