GLASS STRUCTURES AND APPLIANCES. 



283 



angle, which is also the best position for the stoke- 

 hole. 



^iin^nsions, MateHals,and Mode of Comtructiitff Flues. 

 —Ordinary flues (Fig. 72) are generally made ten to 

 twelve inches in width and sixteen to eighteen inches 

 in height internally, more or less, according to the 

 size of the house and the area to be heated. The 

 heating capabilities of flues have been variously 

 estimated ; but as much depends upon the construc- 

 tion and mode of glazing, no very correct data can 

 be laid down. It has, however, been calculated that 

 one fire will heat 3,000 feet to "Vinery temperature 

 if the structure be 

 span-roofed, having 

 all its sides and 

 ends of glass, while 

 in the case of lean- 

 to houses, one fire 

 will heat 5,000 feet 

 to stove tempera- 

 ture. The materials 

 may include good 

 ordinary bricks, fire 

 bricks or tiles, or 

 fire-clay pipes set 

 on earthenware 

 chairs. Stone flags 

 have been used, but 

 owing to the liability of 

 stone to crack under the 

 force of great heat, they are 

 not suitable, neither are 

 they economical. Eire-bricks 

 set on edge make an excel- 

 lent flue, which will last for 

 many years ; but, owing to 

 the great number of joints 

 which they contain, many prefer fire-brick tiles, three 

 feet long, one foot broad, and two and a half inches 

 thick. These tiles should be set on edge, having 

 bottoms and covers of similar dimensions, and the 

 better to secure gas-proof joints, the ends should be 

 rebated or checked as a carpenter would halve together 

 the ends of two planks, and the joints well packed with 

 properly prepared fire-clay or ground mortar. Flues 

 and tanks should be built upon a solid foundation to 

 prevent settlements and fractures, as the safety of 

 the plants depends entirely upon the prevention of 

 the escape of smoke or noxious gas when sulphurous 

 fuel is in course of combustion. Those in hot-houses 

 where the ground has been or is likely to be dis- 

 turbed should be set on arched piers ; but in ordinary 

 green-houses they may be placed on a foundation 

 formed of two courses of common brick laid in grout 

 or concrete. The bottom or floor of the flue should 

 be formed of pavement or tiles resting upon bricks 



set edgeways, as shown in Fig. 72, so as to raise it 

 well above the floor of the house. The object sought 

 in this arrangement is the prevention of damp, which 

 would have a tendency to cool the air in the flue and 

 obstruct the draught of smoke and heat, while the 

 pigeon-hole basement wiU in a great measure do 

 away with the loss of heat by absorption. The best 

 covering is made of fire-clay, quite flat on the upper 

 surface, not hollowed out for the reception of water, 

 which filters through into the interior of the flue, if 

 it does not produce scalding steam of a most dangerous 

 character. Atmospheric moisture is, however, neces- 

 sary, but this is 

 best produced by 

 the use of loose 

 glazed earthenware 

 vessels placed on 

 the covers for the 

 reception of the 

 water. 



Pig. TL— Position o£ Flues. 



I I I 



Fig. 72. — Construction of Flues, 



The Ama- 

 teur's Flue 



When fires for pur- 

 poses not strictly 

 horticultural, as in 

 dwelling-houses,are 

 kept constantly 

 going, and 75 per cent, of 

 the heat passes up the chim- 

 ney, flues equally eflicient, 

 and much cheaper, can be 

 made of the ordinarj' fire- 

 clay pipes nOw so exten- 

 sively manufactured in 

 Staffordshire and elsewhere. 

 The modern glazed pipe 

 now so much used for drainage and sewerage 

 purposes, which we meet with in everj' builder's 

 yard, is perhaps as good an article as anything 

 yet introduced, and, being so extensively used 

 throughout the United Kingdom, can be obtained 

 in stock sizes at a very reasonable price. Well- 

 prepared fire-clay should be used for the joints, and 

 the flue, when finished (with a slight rise, as in hot- 

 water pipes), should rest on brick piers or chairs, at 

 least six inches clear of the ground or other cold 

 substance, which would otherwise abstract a great 

 deal of the heat. 



In small green-houses attached to the dwelling, 

 where economy is imperative, these pipes will fill up 

 a void which has long been felt by thousands of in- 

 telligent men, who derive as much pleasure from the 

 culture of a few cheap plants, shaded by a Vine or 

 two, as the nobleman does from a priceless collection 

 of Orchids. All that is wanted, the professional 



