116 



THE DICTIONARY OF GARDENING, 



Heating continued. 



generated by the combustion of fuel inside a boiler, heat 

 may be conveyed, by water or air, to a considerable dis- 

 tance ; the more remote it is, the less will be the amount 

 that reaches the further extremity. Heated air or water 

 becomes lighter than when cold, and naturally ascends in 

 consequence. Either may be conducted in an upward 

 incline, or in a perpendicular or horizontal direction, but 

 not readily downwards, on account of the disposition of 

 all heated substances to ascend. This transmission of 

 heat in pipes containing water is usually termed circula- 

 tion, and the arrangement of the pipes throughout, to 

 allow an unimpeded circulation, is one of the main prin- 

 ciples of Heating, but is not sufficiently recognised in 

 many instances. The boiler must be placed below the 

 level of any point the heat from it is intended to reach, 

 the upper, or flow pipe, being connected on the top. The 

 return pipe, by which the cold water enters, should be 

 rendered free from the action of the fire by connecting 

 it near the base at the front preferably and on both 

 sides, if this is convenient. Dips in the pipes at any 

 point should be specially avoided, as they frequently im- 

 pede free circulation generally more so when extra heat 

 is applied. Houses erected for various purposes may have 

 their quantity of pipes in proportion to the heat re- 

 quired, and still be in connection with the same mains 

 conducting heat to others having much higher tempera- 

 tures. There are no special rules applicable, in all cases, 

 as to how many pipes a certain house will require, so 

 much depending on stoking, and upon the amount of 

 heat that may be available. It is best to provide for 

 emergencies, in the first place, by insuring a sufficiency 

 of piping, and inserting valves in the flow and return 

 pipes, for regulating the admission of heat. In the 

 arrangement of a Heating apparatus, an important 

 part should be taken by the gardener in charge, as, 

 although the workmen employed may understand the 

 principles on which the success of their work depends, 

 they do not similarly understand the requirements of 

 plants. A proper system must be adopted where there 

 are several houses to be heated and kept at different 

 temperatures, by one or more boilers set and connected 

 together. Main flow and return pipes should be fixed, 

 with a gradual rise, at a point below all others in con- 

 nection, and near the central part of the distance the 

 heat is intended to reach, so that branches may be taken 

 on either side. All houses or pits intended for Heating 

 separately, and irrespective of the one adjoining, should be 

 provided with check valves near the junction with the main 

 pipes. As heat always rises most rapidly to the highest 

 points, it should be arranged that these are in the houses 

 required at the highest temperatures. Pipes 4in. in 

 diameter are those most largely used for top heat; 

 others, only 3in., are well adapted for beds or for small 

 houses. In houses specially devoted to plants requiring 

 a somewhat dry atmosphere in winter Pelargoniums, 

 for instance an extra 2in. pipe is sometimes fixed along 

 the lower part of the rafters for drying the air, this 

 being generally attended with excellent results in the 

 production of large, clean flowers, free from damp. 



Boilers. Of these, there are numerous forms in use. 

 Some are composed of one or two series of cast-iron 

 pipes placed in an upright or horizontal direction, and 

 exposed to the action of the fire. Others are made 

 of welded or wrought iron, and as they can be pur- 

 chased in such a variety of sizes, and invariably answer 

 well, their use is somewhat extensive. The more simple a 

 boiler is in construction, and the greater surface it ex- 

 poses to the direct action of fire used, the better. Tubu- 

 lar boilers frequently become choked with fuel amongst 

 the pipes or tubes, and, if this is not prevented, a great 

 loss of heat is sustained. Boilers having complicated 

 arrangements of any sort are seldom so effective as 

 those of a simple form, the divisions between the 



Heating* continued. 



parts in the furnace soon becoming choked with soot. 

 The requisite size of boiler depends on its approximate 

 Heating power, the length of pipes connected, and the 

 amount of heat required. It is advisable to make pro- 

 vision, in the first place, by fixing a Heating power con- 

 siderably higher than that absolutely necessary. A great 

 deal depends on the sort of fuel used, the rapidity of 

 draught, and the manner of stoking. The plain Saddle 

 Boiler is well known as being one of the oldest types, 

 but, when properly set, still amongst the most efficient. 

 There are various modifications of it, which claim various 

 advantages, such as economising fuel, heat, &c. One 

 of the most useful and efficient forms is the Flue and 



FIG. 172. FLUE AND TERMINAL END SADDLE BOILER. 

 a, Flow Pipe ; 6, 6, Return Pipes ; c, Flue. 



Terminal End Saddle (see Fig. 172). It is a wrought 

 welded boiler, made in sizes varying in length from 

 2ft. to 5ft., heights and transverse inside measure- 

 ments being in proportion. The approximate Heating 

 power of one of these boilers, 2ft. long, is given as 500ft. 

 of 4in. piping ; 3ft. long as 800ft. ; and 5ft. long as 2000ft. ; 

 the unequal proportion, in results corresponding with 

 length, being accounted for by the enlargement of all 

 parts, and the variation in height and width. The flue 

 extends nearly to the back, and through it the whole of 

 the heat must pass from the fire. Sometimes, another 

 flue is formed with bricks on the outside surface, as with 

 the ordinary Saddle ; at others, the whole is covered with 

 an arch without any division. As the full surface of the 

 boiler on both sides is exposed to heat, nearly the fullest 

 possible amount is absorbed before reaching the chimney. 

 The Gold Medal Boiler (see Fig. 173), so named from that 

 award being conferred on it after a working competition at 

 the Birmingham Exhibition in 1872, is of wrought iron, 

 and virtually a flued Saddle with a terminal end, the flue 

 being in the form of three chambers instead of one, 



FIG. 173. THE GOLD MEDAL BOILER. 



as in that previously noticed. This boiler maintains a 

 high position, and a large number are in use. Various 

 sizes are made, ranging from 2ft. to 6ft. long, and pro- 

 portionately large in all parts. The approximate Heating 

 power of one 2ft. long, is 500ft. ; that of 4ft., 1700ft. ; and 

 that of 6ft. in length, 3500ft. all of 4in. piping. 



