STEAM CISTERNS. 



19 



result anticipated ; and others have filled the space with faggots, through 

 which the steam circulated, hut with no better effect. Broken bricks we 

 conclude to be the best material to use for this purpose, as they are 

 better retainers of heat than hard stones, but these may be objected to on 

 account of their being less durable. 



Steam has also been apphed to heat a large cistern of water, placed 

 in the centre of the house, and under where the plants stand. To explain 

 the operation of this process, let us suppose, that instead of a bark 

 bed, a tank of the same length and breadth is substituted, and filled 

 with water about a foot or eighteen inches deep. Through this volume 

 of water a two inch steam pipe is made to enter at one end, and after 

 proceeding to the extremity, is made to return again to the end at which 

 it entered. The steam is let into these pipes about twice a day, and the 

 temperature of the water is ascertained by leaving a small opening at each 

 end, into which a thermometer can be introduced. These openings 

 also answer another purpose, namely, admitting a portion of vapour 

 into the house. Over such cisterns a flooring of bricks is formed, sup- 

 ported upon cast iron bearers, on which the plants are set. Some have 

 recommended stone pavement for this purpose, and others have used 

 boarding, but neither of these are so well calculated for the transmission 

 of heat, as twelve inch tiles. In Stothart's description of this kind 

 of heating, pubhshed in the first volume of the Hort. Soc. Trans., second 

 series, it is recommended, that over a flooring of tiles laid without 

 mortar, a bed of broken stones or bricks, about a foot in thickness, 

 should be laid, broken small, so that those towards the top may not be 

 greater in diameter than about two inches, over this is placed a covering 

 ^ of coal ashes, into w^hich the plants are to be plunged. 



' As we do not advocate the principle of plunging plants in pots, unless 

 under extraordinary circumstances, we confess ourselves at a loss to divine 

 the utihty of either the stones or coal ashes in this operation. 



Steam has also been advantageously applied to heat w^ater contained in 

 tubes laid through plant houses, in a similar manner to flues or hot water 

 pipes. The rationale of this plan is to heat a volume of water by means 

 of steam, to a certain temperature, which will, for a considerable length 

 of time afterwards, continue to give out its heat in a very gradual and 

 gentle manner. As this appears to us to be one of the most rational modes 

 of applying steam as a medium to heating hot houses, we shall quote the 

 following account of it from the last edition of the Encyclopedia of 

 Gardening. It is well kno\^'n," says the intelligent compiler of tliat 

 valuable work, that, by the common hot water apparatus, the heating 



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