[ lSin, 



Memoirs of the Caledonian Horticultural Society. 337 



no other work than to be properly joggled into one another, 

 and jointed with Roman cement. This will give out more 

 heat, and less moisture, than the brick walls, but will not re- 



130 deg. tam tne neat so long. The open space (a a) round the pits 

 must be kept clear of rubbish, which may be done by the 

 covers of the steam-flue being made broad enough to cover 

 it, and neat oblong cast-iron lifting ventilators, in frames, 

 10 in. long, and 2i in. broad, inserted at every foot's distance, 

 into the cover of the flue above the open space. In this 



70 manner, the heat from the sides of the chamber may then be 



given or withheld at pleasure. 



" It is of importance, in the management of steam-pits, to 

 have a thermometer so constructed as to render it easy to 

 ascertain the temperature at the bottom of the earth, or 

 pots, in the plant pit. An instrument adapted for this pur- 

 pose is represented in fig. 58. : the ball and stem are pro- 

 tected by a brass case, the upper part of which is composed 

 of two tubes, cut open wide enough to show the scale ; the 

 outer one turns round by the hand, and encloses the scale, 

 to protect it when the plants are watered with the syringe." 



The Caledonian Horticultural Society voted to 

 Mr. Hay the London Society's medal for 1828, 

 for this improvement. It may, unquestionably, be 

 considered as the best mode of applying steam 

 as a bottom heat ; and when it is considered that, 

 instead of the large pipes of " 3 in. bore," em- 

 ployed by Mr. Hay as mains or conductors, gas 

 pipes of half an inch in diameter will do just as 

 well, this may be considered as perhaps the very 

 cheapest mode of heating hot-houses, or pits on a 

 large scale, hitherto devised. It has also the great 

 advantage of conveying the heat to any distance from the 

 boiler or source, more especially if the latter be placed in the 

 lowest part of the grounds on which the different houses or 

 pits are arranged. For a single house, or two or three houses 

 on one and the same level, the circulation of hot water from 

 an open boiler, by the siphon or level mode, will consume 

 less fuel ; and Mr. Perkins's mode will occupy less space ; 

 but neither of these modes will equal in economy the circu- 

 lation of steam in small pipes. As a proof of this, we may 

 refer to the extensive arrangement of pits in the Bristol Nur- 

 sery, all heated on this principle ; and to Messrs. Cottani 

 and Hallen of Winsley Street, and Messrs. Walker of 

 St. John's Square, Clerkenwell; both of which firms employ 

 this mode of heating, where circumstances render it the most 

 advisable. Indeed, it is one of the most creditable circum- 

 stances connected with these firms, that they are not wedded 

 to any particular mode, but adopt whatever they consider 

 best suited to the particular case. 



We may just observe that we saw, in the summer of 1831, 

 Vofc. VI II, — No. 38. z , 



