London Nurseries. 



375 



the top 12 in. wide. The smoke passes from the flue boiler through its 

 extremity (b), and enters a common brick flue (/), in which it is carried 

 into an upright flue to the chimney top over the fireplace ; or, by means of 

 dampers, it is made to enter another flue (g), and make a return in the 

 back wall, by which it may be fairly presumed as much heat is obtained 

 from the fuel and smoke as is practicable. The heated water proceeds from 



the flue boiler by a horizontal open- 

 ing (h), and enters a shallow tube 

 3 ft. wide, and about half an inch 

 deep (fig. 81.); it proceeds along 

 this tube till it enters a cistern (?) at the other end of the house, from the 

 bottom of which it returns by a cylindrical pipe (fig. 82. k), and this pipe 

 when within 5 or 6 ft. of the fireplace, or lowest 

 point of the boiler (7), divides, so as to return the 

 water in equal portions at the bottom of each side 

 of the boiler (fig. 82. m and fig. 79. n). 



It is evident that by this arrangement very little 

 heat can be lost, and also that the heat com- 

 municated to the water surrounding the fire- 

 place will be very rapidly carried to the cistern 

 (fig. 80. i), at the other extremity of the house. 

 Shoidd it be desirable at any time for the sake of 

 a gentle steam, the covers of the broad shallow 

 tube (fig. 81.) can be taken off", while, when no 

 steam is wanted, the water joint (fig. 83.) is ef- 

 fective in excluding it. This mode of 



constructing these water plat as with a 



water joint gives them a considerable 



superiority over the thin plates of 



Mr. Weekes (Vol. V. p. 544.) ; but 



Mr. Knight's covers are too large for 



being conveniently lifted off and re- 

 placed. This, however, is easily remedied. 



The small quantity of fuel, even shavings, that 

 will heat the water, and the short time required for 

 this purpose, are not a little surprising, and only 



to be accounted for by the extraordinary capacity of water for heat. The 

 same quantity of shavings burnt in a flue, surrounded by brickwork, instead 

 of iron and water, would generate the same quantity of heat, but the brick- 

 work being a non-conductor, a great portion of heat must necessarily be 

 carried along the flue, and unless this is of great length, out at the chimney 

 top. This familiar case must convince the most ordinary capacity, that 

 heating by hot water, besides its numerous other advantages, must produce 

 a very considerable saving of fuel. On the whole, though this plan might 

 certainly be improved on, as far as neatness of appearance, and perhaps also 

 economy, are concerned, it may be considered a valuable variation, and 

 creditable to the spirit and judgment of Mr. Knight. — Cond. 

 , Further Particulars by Mr. Knight himself, dated March 3. — Dear Sir, 

 When you favoured me with a visit and inspected my hot-water apparatus 

 at the commencement of the late severe frost, soon after it was erected, 

 I could not speak positively as to its merits or imperfections, since that 

 time there has been abundant opportunity to prove its efficacy during 

 the long severe winter; and as several of my visiters, who are constant 

 readers of your Magazine, wish much to have a plan and description by 

 them for reference, I beg to offer the following remarks : — What is in 

 reality my boiler is also a flue, which, from the furnace, for 13 ft. 6 in. is 

 on the ascent of nearly 2 in. in the foot, and for 5 ft. 6 in. is on a level, 

 making in the whole 19 ft.; the two sides, which are nearly 18 in. deep, and 



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