272 



CASSELL'S POPULAR GARDENING 



sweetest of all, and for this reason, as well as for 

 their many associations, deserve to be gTOwn in pots, 

 either for forcing or otherwise. 



Other Roses for Pot-culture or for Forcing. 



Noisettes. 



Celine Forestier. 

 Lamar que. 

 Solfaterre. 



Teas. 



Catherine Mermet. 

 Comtesse Eiza du Pare. 

 Homere. 

 Isabella Sprunt. 

 Innocente Pirola. 

 Jean Duclaer. 



Wm. Allen Richardson. 

 Caroline Kuster. 

 Eeve d'Or. 



Madame Bravy. 

 Madame Cusin. 

 Madame Margottin. 

 Madame Welch. 

 Marie Van Houtte. 

 Souvenir d'Elize. 



Syhrid Perpetuals. — In addition to those abeady 

 named for their fragrance, (fcc, the following are 

 a few good varieties for pot-culture: — 



Abel Carriere. 

 Baroness Eothschild. 

 Catherine Souiiert. 

 Comtesse de Serenye. 

 Duke of Connaught. 

 Edward Mon-en. 

 Fisher Holmes. 



Madame Lacharme. 

 Madame Clemence Joig- 



neaux. 

 Mile. Marie Eady. 

 Prince Camilla de Rohan 

 S^uateur Vaisse. 



GLASS STEUCTURES AND 

 APPLIANCES. 



B.EATING. 

 By William Coleman. 



ALTHOUGH heating by the circulation of hot 

 water through metal pipes dates back to a 

 period prior to the Christian era, when the Romans 

 heated their baths by means of coils of pipes which 

 passed through the fire, the method does not seem to 

 have made much progress until the latter part of 

 the last century. More than a hundred years have 

 elapsed since a Frenchman employed hot-water 

 pipes for warming incubators, but the system did 

 not reach this country until 1817, when M. Cham- 

 bannes introduced an apparatus for heating a con- 

 servatory and the rooms in his house. From that 

 time until the removal of the duty on glass, and the 

 introduction of cheap foreign timber, its progress 

 was extremely slow, and the principle being im- 

 perfectly understood, many mistakes and failures 

 were the stepping-stones which led up to the gradual 

 perfecting of a science which now forms the great 

 moving power in our forcing operations. 



Until within the last few years, the old brick flue 

 was the only heating apparatus, and clumsy as it 

 now appears to have been, we gather from reliable 

 authors, independently of our own experience, that 

 excellent crops were forced into early maturity by 

 means of well- constructed brick flues. There is, as 

 all horticulturists know, another method of obtain- 



ing heat, viz., from fermenting materials, but this 

 method has been suflS.ciently treated incidentally in 

 other articles. 



Circulation. — All horticultural buildings are 

 heated upon the low-pressure principle, pure soft 

 water, free from lime, being the best medium that 

 can be used. The apparatus is filled with cold 

 water, which attains its greatest density and smallest 

 volume at 39*2 Fahr. Upon the ternperature being 

 raised above this point, the volume iucreases and the 



Fig-. JrLi. — Circulation of Water. 



density decreases. Let us assume that the boiler a 

 (Fig. 46) is filled with cold water, and the stop- valves 

 a and h are closed. On applying heat to a, the water 

 wiU expand, and the water at the bottom of the 

 boiler after it has been heated and expanded wiU 

 evidently be lighter than it was before. From this 

 cause, even in the boiler, a circulation of the water 

 takes place, the heated particles rising upwards 

 through the colder ones, which sink to the bottom, 

 owing to their greater specific gravity, until they in 

 their turn become heated and expanded like the 

 others. This intestine motion continues xmtil all the 

 particles become equally heated and have received 

 as much heat as the fuel can impart to them. But 

 supposing the two valves a and b are now opened 

 simultaneously, the warm water in the boiler will 

 immediately fiow along the top pipe, c, towards b, and 

 the cold water in the retui-n-pipe will flow along cl, 

 from B to the boiler. In this way the cold water is 

 kept descending to the bottom of the boiler to be re- 

 heated, through the pipes, instead of in the boiler 

 itself. As the water in the pipes is constantly parting 

 with its heat by radiation and conduction, while that 

 in the boiler is as continually receiving additional 

 heat from the fii-e, an equality of temperature can 

 never occur ; if it did, circulation would cease. 



Expansion cisterns in small apparatus like Fig. 47 

 are absolutely necessary, otherwise the expansion of 

 the heated water would defeat the object in view, 

 and in the event of the water boiling, the safety of 

 the boiler might be endangered. Although under 

 good stoking the water should not boil, yet there is 

 always a certain amount of danger. For this reason 

 the expansion cistern, b, should be connected with the 

 lowest part of the return-pipe, when it will also serve 



