376 London Nurseries. 



the top, which averages full 1 ft. wide, are constructed of two plates of cast 

 iron, allowing a cavity for water of three quarters of an inch, presenting an 

 internal surface, on which the fire acts, of 70 ft. superficial, or rather more, 

 and of course giving an equal external surface, which is all within the house. 

 The furnace is of the usual form ; but, instead of brick or tiles, the iron plates 

 and water form the two sides and top, 19 ft. long, at the end of which the 

 smoke is conducted into a brick flue of the common construction. At the 

 extremity of the boiler, connected with the level part, a cast-iron table of 

 3 ft. wide is fixed, forming a right angle, which conducts the hot water to the 

 other extremity of the house, where it passes into a cistern, from the bottom 

 of which it returns again by a common round cast-iron pipe, which branches 

 near the boiler, into which it again returns the coolest water, on each side, 

 close by the fire. The table upon which the water flows rests upon iron 

 stands, and is on a true water level ; it has edges 1 in. deep, so that a thin 

 sheet of hot water three quarters of an inch deep, flows over the 3 ft. sur- 

 face of the table, upon which lids are placed, so constructed as to enclose 

 the steam ; these may be in part or entirely taken off at pleasure, by which 

 dry or damp heat may be obtained, as the various seasons and objects may 

 require, which advantage all practical gardeners know well how to appre- 

 ciate. The rate at which the water moves along the table varies according 

 to the greater or less heat it contains : when at about 140° it moves at the 

 rate of about 10 ft. in a minute. . 



The house in which I have erected this apparatus is new, it is full 50 ft. 

 long, 20 ft. wide, 6 ft. 6 in. high in front, and 16 ft. 6 in. high at the back ; 

 roof glass, containing about 1 150 ft. ; the front is glass about half down, and 

 contains 150 ft.; back and ends are brick, except the doors, and contain 

 about 11,500 cubical feet of area, which by this apparatus has, during the 

 late frost, been kept up to 50° of heat with the most moderate consumption 

 of fuel, in the most severe nights it did not appear to have exceeded from 

 half to three quarters of a bushel of small sifted coals in 24 hours. I am not 

 aware that the water has ever been heated in the boiler to more than 140°, 

 which will appear sufficient when I state the extent of superficial surface 

 from which I derive heat : my boiler is entirely in the house, and presents 

 an external surface of full 70* ft., the table 3 ft. wide, taking the upper and 

 under surface, produces about 300 ft., making together 370 ft., not taking 

 into account the cistern and returning pipe, which present nearly 100 ft. 

 more. The whole quantity of water my apparatus contains is about 70 to 

 80 gallons, on which the fire acts so powerfully and instantaneously that it 

 is set in motion in less than three minutes after the fire is lighted; and I 

 have no hesitation in saying, that it could be made to boil in ten, by stopping 

 the circulation of the water. 



Should the above description not prove sufficiently explicit, I beg to add 

 that it is open to inspection, and I shall have pleasure in explaining, as far 

 as I can, any thing difficult about it. It is, I consider, just and right to add 

 that my apparatus was made and put up by Mr. George Jones of the Phoenix 

 Foundery, Snow Hill, Birmingham, whose attention, liberality, and workman- 

 ship are, I consider, highly creditable to him, and have been entirely satisfac- 

 tory to me. I remain, dear Sir, &c. — Joseph Knight. Exotic Nursery, 

 King's Road Chelsea, March 3. 1830. 



Exotic Nursery, May 1. — The large plants of -Rhododendron arbor eum 

 have now a magnificent appearance in the lofty iron-roofed green-house, 

 which indeed has given a new character to several old plants, by permitting 

 them to attain something like their natural size. Kennedia monophylla, for 

 example, which excites little attention in the common pot, is here planted 

 in the ground, and covers a pillar upwards of 20 ft. high ; few would be* 

 lieve the plant capable of producing such an effect. The orange trees in 

 the house heated by hot water have made vigorous shoots, and are every 

 thing that eould be desired. The choice collection of foreign azaleas is 



