126 Mode of warming and ventilating Hot-houses 



observes in his letter, all forcing will henceforth be a farce where 

 Mr. Penn's mode of heating and ventilating is not adopted. 



5. Mr. Penn's improvement can be added to any house or pit 

 already existing, whatever may be its form or dimensions ; though, 

 of course, with more advantage in the case of some forms than 

 others. Mr. Penn also informs us that a house that has been 

 already heated by hot water or steam can be rearranged ac- 

 cording to his plan, and the same boiler and pipes used. 



6. In the atmosphere of London, where the air is charged 

 with soot and smoke, Mr. Penn's improvement will admit of 

 forming a green-house or stove with much purer air than could 

 be obtained by admitting the external atmosphere according to 

 the usual means of ventilation, which would not only be better 

 for the plants, but for persons going in to examine them. 



Of course such an improvement as Mr. Penn's, which has only 

 been made about three years, admits of an endless variety of 

 modifications. For example, all the shutters to the tubes might 

 be regulated by a self-acting apparatus, so as without personal 

 attention to keep the house constantly at any required tempe- 

 rature. A long cylindrical tin tube, air-tight, placed horizontally 

 against the back wall, with an accurately fitted piston, might be 

 the moving power ; or a thermometer on Kewley's principle, 

 with a cylinder and piston acted on by water supplied from a cask 

 on the top of the wall of the house, as exemplified in ] 819 in Col- 

 vill's Nursery, King's Road, and described in our Encyclopcedia 

 of Gardening, edit. 1835, p. 558. By means of such an appa- 

 ratus, the forcing might go on for days together without any 

 attention from the gardener, provided fuel and water were sup- 

 plied to the boiler ; and by a self-supplying hopper, and the use 

 of coke or anthi*acite coal, the fire would not require attention 

 more than once or twice a day. By a very simple arrangement 

 of the piston of the tin cylinder, or by Kewley's regulating ther- 

 mometer to operate on a piston to be raised by water, a damper 

 might be opened or shut, so as in some degree to regulate even 

 the fire. In this way a gentleman or lady, with the assistance of 

 a house servant, might be in a great measure their own gardener. 

 The common fruit-wall of a garden might have upi'ight sashes 

 placed in front of peach trees or vines, the hot-water pipes 

 placed behind, and the hot air brought up as shown in j^'. 21. 

 Then, if the border were supported on flagstone, like that of 

 Mr. Jedediah Strutt at Belper (see our volume for 1839, 

 p. 44'8.), the whole mass of soil and roots might be heated as 

 completely as if they were in a pot. The border might be 

 covered with horizontal glass, with the exception of a part close 

 under the upright glass, to be boarded as a path ; and under the 

 horizontal glass, pots of strawberries might be placed, early po- 

 tatoes planted, or cucumbers and other dwarf or spreading articles 



