232 Retrospective Criticism. 



I have lately heated a new house, 300 ft. long, and 40 ft. wide, for T. Ashton 

 Smith, Esq., it was not finished till the latter end of November, when the 

 bricks and mortar were all very wet and cold, as well as the ground and 

 drains. The apparatus was put to work as soon as finished : of course it 

 was not to be expected that there would be a sufficient quantity of heat at 

 first, which has been the case in this most extraordinary severe winter ; this is 

 not at all surprising at a time when there has been a general complaint of want 

 of heat under all systems. 



I shall feel great pleasure in showing any gentlemen my houses and plants ; 

 they will then be convinced that the fault is not in the system, though at first 

 I think it was not applied by me in the most beneficial manner. — John Penn. 

 Lewisham, March 15. 1841. 



Mr. Penn's Mode of Heating and Ventilating Hothouses. — From the account 

 you gave of it in the Gardener's Magazine for March, 1840, and my high 

 opinion of the author, I was inclined to become quite a convert to the system, 

 but a recent visit to the seat of T. A. Smith, Esq., Tidworth House, Hants, 

 has quite altered my views on the subject. 



Mr. Smith being a gentleman of immense wealth, and particularly attached 

 to horticultural pursuits, had allowed the system to be adopted to great extent 

 under the immediate superintendence of Mr. Penn, sparing no expense and 

 grudging no sacrifice, to give the system a fair trial. The result, I am sorry 

 to state, terminated in utter disappointment. The heated air from the tubes 

 in place of revolving, as shown by the arrows in your section. Vol. for 1840, 

 fig. 19. p. 122., remained perfectly stagnant and stationary at the top of the 

 house ; and in place of being a " uniform revolving heat," as stated by 

 Mr. Penn, was in reality remarkably partial, and deficient of the desired 

 temperature, had it been general ; as a proof of which, during the late frost 

 the houses and pits were completely covered with a sheet of ice and snow, 

 except a small space at the top directly over each of the tubes (which in this 

 instance were situated inside) ; the branches of the peach trees enjoying the 

 warm air from the mouths of the tubes were in full blossom, whilst the other 

 branches showed not the least symptoms of excitement ; at the same time, the 

 houses and pits requiring a higher temperature could not be raised above 40°, 

 the frost at that time amounting only to 10°. This deficiency, I understood, 

 was at first attributed to the improper attention of the men in charge of the 

 fires. One of Mr. Penn's foremen was immediately sent down, who, after 

 sitting up all night, succeeded in only maintaining a lower temperature than 

 the regular attendants, under similar circumstances. The fuel used there is 

 the anthracite coal. Lest the desideratum should have arisen from fresh 

 damp materials, absorption, and the like, a patient and protracted trial of a 

 couple of months was still persisted in, after which the necessity of abandoning 

 the system was deemed indispensable. The exposed pipes and movable sashes 

 are now resumed and accompanied by their anticipated favourable results. 

 A little reflection might possibly convince any one of the impracticability of 

 keeping the sashes screwed down, as advised, during a scorching summer's day. 

 The powerful boiler erected by Mr. Penn still remains, and is much approved 

 of, performing that work with ease, which, during the concealment of the pipes, 

 it was incapable of. 



A large span-roofed conservatory, 300 ft. in length by 40 ft. in breadth, has 

 during the past autumn and winter been erected at Tidworth House, for the 

 culture of both horticultural and floricultural productions, and also to furnish 

 an agreeable retreat and promenade for the family during the winter months. 

 The interior contains two large longitudinal beds, or borders, interrupted by a 

 circle of gravel and a transverse walk in the centre of the house, one broad 

 gravel walk in the middle, and two narrower ones on either side. It is heated 

 by Mr. Penn from one large boiler ; the hot-water pipes are arranged under 

 the centre of the two borders, transmitting heated air to the house by means 

 of cyhndrical metallic tubes, about 20 ft. apart; a line of circular gratings in 

 the centre of the three gravel walks, intended to receive the cold aii', com- 



