THE PINE-APPLE. 



33 



invidious to recommend any particular maker or 

 kind of boiler to those who are quite capable of 

 choosing for themselves. But for the benefit of 

 amateurs and others who are bewildered by the 

 endless variety now in commerce, it is only fair to 

 say that, after many years' experience, the old saddle 

 boiler in its improved form — that is to say, welded, 

 not cast — with its terminal water-way end, still 

 stands unbeaten. 



Equal in durability, and perhaps superior in 

 power where the work is very heavy is Stevens' 

 Trentham or improved Cornish boiler. This, too, 

 is made of wrought-iron, and, like the saddle boiler, 

 can be obtained in almost any size ; but as it is bad 

 policy to trust all the eggs in one basket, so is it a 

 great mistake to trust the contents of a range of 

 hot-houses to one boiler, as the very best are liable 



Pig. 3.— Spah-koofed House. 



A, Plunging-bed ; B, drainage ; c c, ventilators ; d, pas= 

 sagri ; o o, pipes ; e e, tot-air chamber. 



to accidents, and d. break-down on a frosty night 

 means the destruction of valuable property. To 

 provide against such mishaps, the prudent engineer 

 will put in two boilers of moderate size, to work 

 separately or together, in preference to having one 

 large boiler, which is not economical in fuel when a 

 minimum of heat is required in summer. In low, 

 wet situations, where floods or back-water cause 

 trouble, boilers which require deep stoke-holes should 

 be avoided : a powerful point in favour of the boilers 

 in question, as each of them requires only a very 

 shallow setting. 



Next in importance is a liberal supply of hot- 

 water piping, for keeping up the proper degree of 

 heat, without forcing the boilers or overheating the 

 pipes in severe weather. It will therefore be wise 

 to put in as many pipes as will answer the purpose 

 without putting on high pressure, and so endanger- 

 ing the health of the plants by subjecting them to 

 a dry scorching atmosphere. Hot-water pipes four 

 inches in diameter are the best for horticultural 

 purposes, and they should be plentifuUy suppHed 

 with evaporating troughs for giving ofE atmospheric 



a? 



moisture, either from pure water, clear liquid manure 

 or guano-water, when a stimulating vapour is con- 

 sidered necessary. The bottom heat pipes, as shown 

 in the sections, run parallel to each other in a con- 

 fined chamber, covered with slate for bearing the 

 weight of the plunging-bed. Some growers prefer 

 laying them in a bed of rough gravel, and so dis- 

 pensing with the hot-air chamber, while others lay 

 them in shallow brick troughs, which are lined with 

 cement, and by being kept full of water, form what 

 is termed the "tank" system of heating. "Where 

 the pot system of growing Pines is strictly adhered 

 to, and tan or, better still, sound Oak-leaves are used 

 as a plunging medium, the tank system answers 

 very well. It is not, however, so well adapted for 

 giving the necessary bottom heat to Pines when 

 they are planted out in a bed of soil resting imme- 



Fig. 4— Pbopabating Pit. 

 A, Plunging-bed ; B, drainage ; c fl, ventilators ; d, pas- 

 sage ; o o, pipes ; e e, hot-air chamber. 



diately above the open tank, as the vapour which is 

 constantly rising in course of time produces a wet, 

 pasty condition in the lower part of the bed, quite 

 unfavourable to the roots, iE it does not positively 

 kill them. If hot-water pipes alone are used, they 

 should be fitted with stop-valves for shutting off 

 and regulating the heat, and tanks require an inlet 

 and outlet tap for filling or emptying at pleasure. 

 In days gone by, the necessary bottom heat was 

 obtained from fermenting, materials alone, and 

 notwithstanding the fact that sudden fluctuations 

 and frequent renovation added considerably to the 

 expense of Pine- growing, it is still a question 

 whether the conditions produced by constant fer- 

 mentation and the decay of vegetable matter did 

 not meet the requirements of the plants in a manner 

 and to an e-xtent which hot water alone cannot 

 supply. With these facts before me, it has long been 

 my practice to combine the two systems, by placing 

 the pipes in chambers, and using Oak-leaves as a 

 plunging medium. 



Covering. — Economy combined with high pres- 



