Forcing-Pit heated hy liot Water. 14-3 



the size above recommended be employed, there will not be 2° 

 difference between the front and back of the pit. In order the 

 better to disperse the ascending currents, it may be well that the 

 aperture, instead of opening directly into the pit, should have 

 a semicylindric draining-tile placed in front of it, to throw its 

 draught right and left : but this is an unnecessary refinement; a 

 pair of 4-inch pipes will, I believe, be found sufficient for cucum- 

 bers, melons, or pines, in a 6-foot pit. My experience shows me 

 they will produce 30° of temperature, which, as such pits are 

 always covered at night in frosty weather, would be quite suffi- 

 cient, except for very early forcing; for which purpose two pair 

 (i. e. four rows) of 3-inch pipes would be preferable. 



There is one portion of the above-suggested plan so evidently 

 borrowed from an arrangement employed by Mr. Penn of 

 Lewisham, at Wilmot's of Isleworth, and probably elsewhere, 

 that it appears due to Mr. Penn both to acknowledge the source 

 from which it is derived, and to point out, at the same time, 

 wherein I conceive the proposed plan an improvement upon his. 



Mr. Penn lays his pipes in flues, or tunnels, as above described, 

 either at the front or back of the house, and causes the air to 

 circulate in tunnels passing under the house. The arrangement 

 is ingenious, and the circulation very complete ; but considerable 

 expense is incurred, and it does not appear that any great advan- 

 tage is attained by it. It is stated that a very salutary circulation 

 of air is obtained ; but precisely the same circulation takes place 

 in every house heated by pipes, only more freely if the pipes are 

 not encased : any one who has steamed a house by syringing the 

 pipes can bear testimony to the rapid circulation of the atmo- 

 sphere, ascending along the roof, and descending by the back, till 

 it returns across the house, or along the floor to the pipes. 



Now, in the arrangement of the pit above suggested, there is 

 a reason for encasing the pipes in a flue ; viz., to obtain from 

 them bottom heat, an advantage neither obtained nor sought in 

 Mr. Penn's arrangement. A collateral advantage is the getting 

 rid of the pipes, which are always exceedingly in the way in a 

 small pit, burning up the plants near them. A third great advan- 

 tage is, the constant supply of moisture brought up from below 

 by the air, all the moisture of the pit draining down to the pipe 

 flue ; and a fourth, the regular circulation, an advantage which 

 I am not disposed to despise, though I do not think it of such 

 value as to be worth much expense in attaining. 



In conclusion, I would remark that any existing pit may be 

 fitted up on the principle above recommended, simply by build- 

 mg a centre flue, and forming the cross and ascending flues of 

 draining-tiles. 



It may be objected to this plan, that the ascending flues should 

 be at the front rather than at the back, lest the upper part of 



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