THE GERMAX FLUE. 



15 



same authority, were found to be inferior to the most ordinan^ description 

 of flues then in use. Indeed, the latter improvement, viz,, the hot air 

 flue, the late Nicol proved to be worse than useless." 



Formerly, flues were built partly under ground ; only the better con- 

 structed ones of that period were above it, but not separated from it, a 

 circumstance which kept them continually damp, impeded the di-aught, 

 and lost a very considerable portion of the heat. Succeeding improve- 

 ments suggested the propriety of not only building all flues upon arches, 

 or a soUd foundation of brick work, but also of elevating the flue one 

 brick or more above the level of the borders. This was the last and 

 most important improvement in the erection of flues. ^Ye may, however, 

 here observe, that cast iron plates were recommended as covers for flues ; 

 and also pavement stones, as well as tiles, both plain and hollowed out, to 

 hold water for the purpose of steaming the house. The former of these 

 are veiy objectionable ; the second very good, when stone of a quahty 

 capable of standing the heat to which flues are exposed can be procured ; 

 and the thu'd and fomth, for general purposes, the best of all. 



Flues constructed entkely of flag stones have been tried, but it is 

 difficult to procm-e stone calculated for this pui'pose, besides, no stone with 

 which we are acquainted, is so well adapted for the transmission of heat, 

 as well prepared and not over humt tiles and bricks. 



No flue should be plastered, either TNithin or ^vithout, as plaster is a 

 bad conductor of heat, and, therefore, very unfit for the purpose. 



Various other sorts of flues have been since recommended by difi'erent 

 writers in the Horticultural Soc. Trans, and elsewhere ; but as they are 

 mostly modifications of those abeady noticed, it would be superfluous 

 ^ to attempt their descriptions. 



The best of all flues are those most commonly in use in well 

 ordered houses : they are built of thin well bm'nt and regular sized 

 bricks, placed on edge, and neatly jointed with well prepared moitar, but 

 neither plastered inside nor out. Such flues vary in their dimensions 

 from nine to twelve inches in ^idth inside, and from fourteen to eighteen 

 inches in height. They are always covered vdth. tiles,- either plain, 

 or hollowed out for holding water, or with flag stones of a description 

 calcLilated to stand the heat. In most cases, the flue should enter thi'ough 

 the back wall at one end of the house, pass on to mthin two or three 

 inches, or morej (according as space vriU admit) of the front wall or 

 parapet, nni parallel with it to the extremity of the house, pass round the 

 farther end, and return parallel to the back wall, and Aritliin two or three 

 inches of it. Or, after having reached the extremity of the house, the flue 



