172 



HEATING AS APPLIED IN HORTICULTURE. 



produces a circulation which continues as 

 long as there is heat in the water. Heat 

 is given out to the house by radiation 

 from the outer surfaces of the pedestals, 

 and circulation of heated air through the 

 tubes in the centre of the latter. 



Johnston's mode of heating. — A very simi- 

 lar mode of heating, by employing pedes- 

 tals or cylinders as the means of diffusing 

 heat by radiation, was, long prior to Mr 

 Walkers invention) practised by Mr 

 Johnston, gardener to his Grace the 

 Duke of Wellington. The water was 

 heated in two small copper vessels placed 

 within an Arnot's stove slightly altered. 

 From these it was conveyed in pipes so 

 connected with union joints that they 

 might be taken to pieces to alter their 

 position, or be removed altogether when 

 not required. The stove is placed in a 

 niche in the back wall of the conserva- 

 tory, or it may be placed under the floor 

 if more convenient. Along the floor of 

 the house upright cylinders are placed; 

 but these might advantageously be re- 

 moved, and highly ornamental vases sub- 

 stituted. The water is led to each by 

 means of a small pipe, with a correspond- 

 ing one for its return to the boiler. Each 

 of the cylinders is 18 inches in diameter, 

 and the same in height, and has thirty 

 tubes 1 inch in diameter placed inside, 

 of a height equal to the height of the 

 cylinders. The water is supplied by a 

 valve near the top of the cylinders, 

 covered with an ornamental cup, which 

 is movable. Heat is thus given off by 

 radiation from the surface of the cylinders. 

 As in Walker's method, the air which 

 passes through these tubes becomes 

 heated in consequence of being surround- 

 ed by heated water, and is in this modi- 

 fied state admitted into the house. It 

 appears that such an apparatus as we 

 have described has been found sufficient 

 to heat the conservatory at Strathfield- 

 saye, 67 feet in length, 27 feet broad, and 2 1 

 feet in height. The consumption of coke 

 for such a stove is exactly one bushel per 

 day, half of which is supplied in the morn- 

 ing, and half in the evening. In regard to 

 priority of invention in the case before us, 

 there is no doubt Mr Johnston is entitled 

 to it rather than Mr Walker — the princi- 

 pal difference between the two being, that 

 Mr Walker places his pedestals on the top 

 of the flow-pipes of an ordinary hoi- water 



arrangement, while Mr Johnston attaches 

 his cylinders by means of small pipes, 

 through which the hot water flows. In 

 the former case the pedestals are fixtures, 

 while in the latter they can be removed 

 with the greatest facility. The idea of 

 increasing the command of heat by ra- 

 diation from either pedestals or cylinders 

 is good; and for conservatories, which re- 

 quire so little artificial heat, we think 

 that this principle might be applied with 

 great advantage and effect by having hot 

 water brought under the floor, and made 

 to circulate through ornamental vases 

 distributed through the house, which, 

 when not required for this purpose, could 

 be filled with plants. The actual utility 

 of the pipes within the radiators em- 

 ployed by both these gentlemen, we think 

 very questionable — for water will circu- 

 late in a vase, and, we think, give out as 

 much heat by radiation from its surface 

 as will be found sufficient, without the 

 complication of these external tubes at all. 



There are various modes by which con- 

 servatories, greenhouses, &c, may be 

 heated upon very similar principles to the 

 above ; and in the former case, where ele- 

 gance of form and design is, or rather 

 ought to be, a consideration, we cannot 

 offer a better example than fig. 206, 

 given in Walker's " Hints on Ventila- 

 tion," &c, who says, " When it is neces- 

 sary that the heating surface should 

 stand within the apartment to be warmed 

 by it, a very compact arrangement has 

 been devised and patented, in which the 

 conducting property of iron has been ad- 

 vantageously employed by the use of 

 square blocks perforated all through from 

 top to bottom by square openings or cells, 

 with their divisions between them. Seve- 

 ral such blocks " (according to the space 

 to be heated, and the temperature re- 

 quired) " are enclosed in an iron case or 

 box, open at top and bottom; and heat 

 being applied to the outside of each block 

 by the introduction of steam or hot 

 water, the entire mass of each block be- 

 comes heated, and imparts heat to the air 

 contained in its cells, which then rises 

 into the apartment, its place being sup- 

 plied, and a continuous current main- 

 tained, through any fresh-air flue over 

 the mouth of which the set of blocks may 

 be placed." In the case of hothouses, this 

 supply can readily be obtained by bring- 



