10 



ROYAL HORTICULTURAL SOCIETY. 



II. Hypocaust-Heating. By C. Wykeham Martin, Esq. 



Having- met with several discussions on the subject of providing 

 bottom-heat for various horticultural objects, I was induced some 

 time ago to turn my attention to the most economical mode, con- 

 sistent with efficiency, of obtaining that which appeared to be 

 very generally desired. I saw that various methods had been 

 adopted, at varying cost and with varying success, and this had 

 taken place more particularly with reference to vine-borders. 

 Arches had been constructed beneath them, into which hot air had 

 been admitted ; but this appeared a very expensive mode, both in 

 its first construction and in its subsequent working, as large 

 quantities of fuel must be used to heat the brickwork sufficiently 

 to be of any service for purposes of cultivation. Hot- water pipes 

 had been passed through borders, but it did not seem easy to 

 diffuse the heat equally by such means, though much has doubt- 

 less been done by placing rubble over the pipes to enable the heat 

 to circulate. Then came the experiments for other purposes by 

 Captain Clarke, of which an account was given in the ' Proceedings 

 of Eoyal Hort. Soc' vol. ii. 1861. His apparatus consisted of a 

 long pit of brickwork five or six feet wide, covered with slates 

 resting on iron bars, and warmed by a three-inch pipe passed down 

 the centre. This seems to have acted extremely well for the pur- 

 poses for which it was designed ; but the slates appeared to be a 

 fragile support, rather adapted to temporary and experimental 

 than to permanent use, and not smoke-proof. 



After much consideration, I determined to try a cheap imitation 

 of the mode in which the Romans heated the principal apartments 

 of their villas. I was aware that builders were much in the habit 

 of using, for roofing-purposes, a covering of three courses of ordi- 

 nary roofing-tiles, laid in cement instead of mortar, and that this 

 substance would bear a considerable weight, if resting on a rigid 

 support at intervals not greater than 6 feet. I therefore adopted 

 in a new house which I was building, the following arrange- 

 ment. 



I first excavated a chamber 2 feet 6 inches deep, at the foot of 

 my garden-wall, and in it built up pillars of brickwork 9 inches 

 square, to that height above the ground. These were about 3 feet 

 9 inches apart in one direction, and rather less than 3 feet in the 

 other, so that at no point was the bearing quite 6 feet. These 

 formed the supports of the floor, which was constructed on a 

 staging of wood, which was removed as soon as the cement had 



