OF BOTTOM HEAT. Ill 



which his Pine-apple and other stove plants grew, 

 without bark or other hot-bed, usually varied from 70° 

 to SS** ; and that the mould in his pots, being sur- 

 rounded by such air, acquired and retained, as it ne- 

 cessarily must, very near the same aggregate tempera- 

 ture, but subject to less extensive variation {Gard. 

 Mag., V. 365) : in another, he says the temperature of 

 the air was varied in his stove generally from about 

 70° to 85° of Fahrenheit ; and he ascertained, by 

 keeping a thermometer immersed in the mould of the 

 pots, that the temperature of the soil varied very con- 

 siderably less than that of the air of the stove ; the 

 mould being in the morning generally some degrees 

 "warmer than the air of the house, and in the middle 

 of the day, and early part of the evening, some de- 

 grees cooler. {Hort. Trans., vii. 255.) 



It is, therefore, clear that he considered a high tem- 

 perature necessary for the roots of his Pine-apple 

 plants ; and we find, from one of his papers, {Hort. 

 Trans., iv. 544,) that he considered it better to obtain 

 the requisite temperature from the atmosphere than 

 from a bark-bed, the usual source of bottom heat, " be- 

 cause its temperature is constantly subject to excess 

 and defect ;" and he even admitted that if the bark- 

 bed could be made to give a steady temperature of 

 about 10° below that of the day temperature of the air 

 in the stove. Pine plants would thrive better in a com- 

 post of that temperature than in a colder. 



It is, therefore, plain that the dispute about bottom 

 heat was not as to the necessity of it, but as to the man- 

 ner of obtaining it, which, as it concerns the art of 

 gardening, I need iiot further notice. 



