Cheshunt Cottage. 663 



The following memorandum respecting the heating of the 

 hot-houses and pits at this place has been kindly supplied by 

 Mr. Harrison. 



" The hot-water apparatus first used in the small house in the 

 walled garden, 3 injig. 159. in p. 652., was put up by a regular 

 mechanic from London, but worked so ill and with such frequent 

 failures, requiring night-watching, that soon after Mr. Pratt be- 

 came head gardener the whole was taken to pieces, and the 

 materials, with additions and alterations, and removing the 

 boiler from the house into an adjoining place where the fire and 

 flue were built, were reconstructed, and the house has com- 

 pletely answered ever since. 



" Since that time no person supplying hot-water apparatus has 

 ever been consulted, or even employed, except in casting boilers 

 and other iron work, according to plans and drawings made to 

 a scale and sent to London ; these materials being put together 

 by a smith in the country, who has learned to cut and join 

 pipes. Three fires heat eight distinct houses ; and if the whole 

 had been erected, or its erection contemplated, at the same time, 

 two fires would have been amply sufficient, by placing the houses 

 requiring most heat nearest the fires. One of the boilers is a 

 common large iron coal box, which has now been in use 

 seven years, without the slightest failure. Simplicity in con- 

 struction, with large bodies of water and iron (the pipes in the 

 largest house being 6 in. internal diameter, in the others 4 in., 

 and going entirely round the pine and orchideous houses, requir- 

 ing the greatest heat, and round three sides of the botanic house), 

 has been the basis of all the plans ; and experience derived from 

 the house in the walled garden has led to the exclusion of all 

 the boilers from the other houses, the delivering and return 

 pipes being in every instance carried from the boilers through 

 the wall, and close fitted ; and experience has proved that the 

 advantages of this mode more than compensate, in various ways* 

 for the loss of heat which the boilers would give in the houses. 



" Experiments have also proved that the 6-inch pipes in the 

 botanic house, which is considerably more than double the area of 

 the pine-house which is heated from the same boiler by 4-inch 

 pipes, give a greater heat than would be given by a double set of 

 4-inch pipes, making full allowance even for the excess of water 

 beyond the double quantity carried by the 6-inch pipes above the 

 4-inch, calculated on the squares of their diameters. This proves 

 that the same quantity of water is more effectual when distributed 

 in large pipes, than in a greater number of smaller pipes. No 

 deficiency has been found in the regular diffusion of heat, and 

 great advantage in the continuance. The pipes through the wall 

 delivering and returning the water in the orchideous house, which 

 supply two sets of service pipes branching off at opposite right 



