The double stopcock will afford the means of occasional separation of the bag, and of examination of the contained air under the influence of different circumstances.

In the section fig. 18. a shows the check or rebate in the top, which lifts up, and is faced with wash-leather; b, the drip for the condensed moisture from the glass; c, the glass frame screwed down on the soil box, with a slip of wash-leather between them; d, the soil in the box; e, the lining of lead, with an inner lining of thin wood; f, the bottom of the soil box; and g, the frame on which the whole rests.

As before observed, I planted the case with some hundreds of bulbs of various sorts on December 28.; and, at the same time placed some of the same bulbs in earth in garden pots, and others in water glasses. Those in the case are distinctly gaining on those in the pots and glasses, and will flower before them. The case stands in a window, facing a little to the eastward of south, and gets what sunshine the season affords. There is no fire in the room, and the temperature near the window rarely exceeds 60°; the pots and glasses are in a window looking N.N.W., but have the advantage of from 2° to 3° of higher temperature during the day; in the night time the whole house is nearly uniform, at from 57° to 60° [being heated by one of Silvester's cockles, as will be described in our Supplement to the Encyclopædia of Cottage Architecture].

I have heard lately of some curious cases of the roots of plants running to a distance in search of bones, and then insinuating themselves into every crevice within them. I recollect also observing at Malmaison that many plants which had been inserted in skulls of animals, were flourishing in a remarkable manner. This leads me to ask you whether bones and bone-dust have been much tried in horticulture, and whether you would counsel me to try some in the case, when in May next it is prepared for its permanent inhabitants. [We shall be glad of a hint on this subject, or on any other relative to this article, from any correspondent.]

Edinburgh, Randolph Crescent, Jan. 20. 1840.

ART. IX. Some Account of a Mode of warming and ventilating Hot-houses invented and applied by John Penn, Esq., Engineer, &c., at his Residence at Lewisham, in Kent. By the CONDUCTOR. THE first attempt that was made to heat hot-houses by hot air was, we believe, made by Dr. Anderson, in a green-house attached to his dwelling-house at Isleworth, about 1802, as described in his Description of a Patent Hot-house, published in

The next was by Mr. Stewart, in the large conservatory at Mr. Angerstein's at Blackheath Park, about 1803, for which a patent was taken out by Mr. Stewart. Both these houses we saw in 1803. Neither of these modes of heating by hot air was considered at the time as completely successful: in one case, we believe, because the air was heated by smoke flues, and consequently was too dry; and in the other, on account both of the means (the heat of the sun) and the arrangements being inadequate. Some time afterwards, but at what period we are uncertain, the Messrs. Strutt of Derby applied their cockle to heating hot-houses by a current of air brought from without, with a power of stopping the supply from without, and reheating the air of the house. A vinery at St. Helen's, the seat of Edward Strutt, Esq., M. P., and one at Bridge Hill, Belper, the seat of George Strutt, Esq., continue to be so heated; and Jedediah Strutt, Esq., has recently heated several hot-houses by this mode, at his residence in the village of Belper, which, as observed in our volume for 1839, p. 448., appeared to answer perfectly, when we saw it in May last; an arrangement being made by which the heated air passes over water, and thus becoming charged with moisture, the defect attendant on all the preceding modes appeared to be remedied. The large conservatory at the Grange was heated by hot air from one of Mr. Strutt's cockles combined with steam, by the late Mr. Sylvester, in 1825, as noticed by us in our first volume, p. 112. Such is the amount of our present recollections on the subject of heating hot-houses by hot air.

Mr. Penn's mode of heating and ventilating by hot air differs from the above modes, in the heating body being pipes of hot water, and in the great simplicity of the arrangements. It appears to us to effect the object much more completely than by any other mode that we have seen; the great simplicity of the arrangements being such, that, as it appeared to us, no repairs can be required for a number of years to come, not, indeed, till the pipes are worn out. This constitutes its superiority to the mode of heating at Belper and the Grange, which appeared to us rather more intricate.

The section, fig. 19., will show Mr. Penn's mode of heating almost without explanation. The pipes of hot water which heat the air are shown at a; the opening by which the air enters the house, at b; c is a grating by which the air is drawn in again, and conveyed along the drain d, to be reheated by the pipes, and again rarefied so as to reenter at b. By these simple and obvious means, the air is in a state of continual circulation, as shown by the arrows in the section. The degree of heat in the house is regulated by shutting, partially or wholly, the openings (b) by covers which are fitted to each. The drains (d) are made at greater or less distances according to the heat required; and, when

1840. MARCH.

K

19

extra-moisture is wanted, water is poured through the grating (c), so as to cover the bottom of the drain. In Mr. Penn's hot-house, in which he grows orchidaceous plants, the drains are about 6 ft. apart, about 18 in. deep, and 1 ft. wide; in his green-house, they are about 12 ft. apart; and in his pine-pit, the pines being plunged in tan, they are about 7 ft. apart. In a span-roofed hot-house for botanic or stove plants, the hot-water pipes are ranged along the centre of the house; and the tubes in which the hot air ascends from the pipes are of boards, and fixed immediately over them, under the ridge of the roof, with their tops reaching to within 2 ft. of the glass. In the pine-stove, the hot-water pipes are under the back path, and the tubes, which are of boards about 18 in. broad, by 9 in. deep, are placed against the back wall in the inside of the house, each having a cover that takes off by the hand. In those houses that have back sheds, the tubes are in the outside of the back wall, as shown in fig. 19. at c. The shed has a double roof to retain the heat; and the border, shown at f, is used for forcing sea-kale, rhubarb, &c., and for raising small salading. Care is taken in forming the drains that they shall open to the pipes, not directly under the upright tubes, but in the space between them, as shown in fig. 20., in which g g are the drains; h, the situation of the gratings over them; i, the situation of the tubes; and k, the hot-water pipes. The object of this arrangement is, to allow the air from the drains to pass a short distance along the hot-water pipes, so as to be reheated before it ascends to enter by the openings b. When it appears desirable to change the air of the house, this is not done by opening the sashes in the usual way, but by taking the stoppers out of two openings into the back drain which contains the hot-water pipes, one at each end, and communicating with the open air. These openings are so small, that each may be filled up with a brick, and made air-tight by a little clay. It ought to be observed, that the wooden tubes by which the hot air ascends are all made perfectly

20

h

air-tight; those in the sheds, being of rough boards rudely joined, have the joints covered with strong paper pasted or glued on: if the openings were carried up in the wall, of course this case would not be requisite. This description and these diagrams have been made entirely from recollection of a visit made to Mr. Penn, in company with Mr. Wilmot of Isleworth, on February 5th, in which Mr. Penn kindly showed and explained everything; and therefore they must not be considered as exact, but merely as giving a general idea of what has been effected.

Though Mr. Penn only began his improvements not quite three years ago, and has not yet completed all his experiments, he has already heated several hot-houses for different noblemen and gentlemen by his mode; and some, such as one at Syon House, have been heated after Mr. Penn's mode (though imperfectly), by others who have seen or heard of it, and endeavoured to possess themselves of the invention, without understanding it. Houses have been heated by Mr. Penn, for the Earl of Clare, in Ireland; the Earl of Dartmouth, Blackheath ; Charles Perkins, Esq., Southend, Kent; Palmer, Esq., Bromley; Keats, Esq., Forest Hill; General Sir More Disney, Acton; Charles B. Curtis, Esq., Acton; John Wilmot, Esq., Isleworth, and others. He has also warmed the dwellinghouse of B. Wood, Esq., M. P., Eltham Place; and that of Crowley, Esq., Croydon; as well as his own billiardroom, at Lewisham. All Mr. Penn's plant-houses at Lewisham, as well as his billiard-room, though scattered up and down his garden, are heated from one small boiler.

It may be useful to state that Mr. Penn, being an engineer, and in a very large way of business as a manufacturer of steamengines, and all sorts of machinery, and having large iron-works, being a man of large property, and being, besides, most anxious

and enthusiastic for the propagation of his plan, will carry it into execution in any part of the United Kingdom at less cost, and, as being the inventor, more successfully, than is likely to be done by any other person whatever.

We shall now state what we consider to be the principal advantages of Mr. Penn's improvement.

1. The heat of air in motion, whether dry or charged with moisture, is never felt by the human body to be so hot or oppressive as when it is stagnant. This every one will recollect to be the case, when he thinks of what were his feelings during a hot summer's day, when there was no breeze, and when there was a breeze. We could not have believed that the difference would have been so great in a hot-house, had we not experienced it. We remained in Mr. Penn's orchidaceous house about half an hour, with the temperature about 80°, and in his pine-pit about the same time, without feeling the slightest inconvenience; so much so, that we could have passed the day, with pleasure, in such a temperature. We felt as if we were in the open air, in a fine summer's day, and experienced none of the disagreeable effects of stagnant and sometimes fetid air, which are so often experienced in hot-houses, particularly in those in which the Orchidacea are grown. The same thing, Mr. Penn observed, had been noticed by a number of persons, including ladies, who stated that they could never remain more than a few minutes in their stoves at home, while they could have remained all day, and even slept, in Mr. Penn's. An analogous effect was experienced at the North Pole, by Captain Parry and his companions when the air was perfectly still, the extreme cold of that region was bearable; but the moment the slightest breeze arose, it became intolerable. We had no means of trying the moisture of the air by a hygrometer, but that the moisture must have been considerable, was evident from the water in the drains, and the dew on the plants.

This alteration in the sensible effect produced by hot moist air on the human frame, we consider to be the great advantage of Mr. Penn's improvement, because it will henceforth render plant stoves of every kind, including even orchidaceous houses, fit for being entered into, and even lingered in, by the most delicate, as well as the most robust, constitutions.

2. By the circulation of the air, blossoms of every kind will be made to set better, fruit will be produced of higher flavour, and leaves and blossoms of more intense colour. We had a proof of these results. In one house there were strawberry plants in pots just going out of flower, and Mr. Wilmot, who was present, declared that the fruit was as well set as if the plants had been in the open air, though the sashes of the house had not been opened, nor any fresh air admitted but what entered through