582 Application of Hot Water in Heating Hot-houses. 



be less than eight, nor greater than sixteen square feet, and 

 the bottom surface four times the area of the grate, with 

 thirty-two feet of side flue ; and a considerable advantage 

 results from adopting the larger proportion for the grate and 

 bottom surface, on account of the fire requiring less attention. 



22. The forms of boilers may be varied in a considerable 

 degree, provided the above quantity of surface receives the 

 effect of the fire ; the first kind used by Mr. Atkinson, was 

 a parallelepiped with the fire applied to the base only. I 

 have employed the same form, but of greater length in res- 

 pect to its width, hence of less capacity, and made the flue 

 go round the sides of the boiler ; it is then of great length, 

 and very effective, and this I consider the best and most 

 simple plan for an open topped boiler, serving as a partial 

 reservoir of heat. A boiler in the form of half a hollow cylin- 

 der, affording a great quantity of fire and flue surface, is made 

 by Messrs. Bailey, (fig. 5) and a bottle-shaped boiler (fig. 6) 

 is made by Messrs. Cottam and Hallen, which has a con- 

 siderable quantity of fire and flue surface, compared with its 

 capacity; both these are, therefore, well adapted to cases 

 where only a small reserve of heat is required for night. The 

 variation of the Scotch distiller's boiler, (fig. 7) is also a good 

 form for maintaining the supply of heat to the house, while a 

 separate reservoir is warmed by part of the pipes. Another 

 mode of obtaining a large portion of fire and flue surface to 

 a small capacity, is shown in (fig. 9,) but complicated forms 

 have little to recommend them, and are expensive except 

 when so small as to be cast in iron, because the fire should 

 be partially surrounded by slow conductors of heat to prevent 

 the dissipation of heat being too rapid, and to render the 



