C 214 ] 



XXII. On the Construction of Flues of Hot-houses. In a 

 Letter to the Secretary. By Sir George Stewart 

 Mackenzie, Bart. F. H. S. 



Read September 18, 1821. 



Sir, 



Th e Construction of Flues has been a frequent subject of 

 consideration with me, since I communicated* to the Horti- 

 cultural Society what is now considered by many to be the 

 best form for the roofs of hot-houses of all descriptions. This 

 is a subject which admits, most readily, the application of 

 scientific principles ; yet we are slow in making improvements, 

 even when the principles on which we must proceed are ob- 

 vious. The causes of our being slow may perhaps be found 

 in the necessity of attending to various circumstances of con- 

 venience, and to the materials to which we have easiest 

 access, as well as in our attachment to habit. The objects to 

 be kept in view, when we attempt to improve the construction 

 of flues, are, the occupation of as little room as possible, con- 

 sistent with the production of the amount of heat required ; 

 facility in cleaning them, in removing and setting them up, as 

 well as in repairing them ; economy in the materials ; durabili- 

 ty ; and lastly, that the materials shall be such as to give out 

 heat readily. 



In many parts of the kingdom, it is difficult as well as ex- 

 pensive, to procure bricks and tiles for flues of the most ordi- 



* See Horticultural Transactions, Vol. II. page 171. 



