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the laps of the glass or by the occasional opening of the door, since the strawberry plants were introduced. Some queen pines had ripe fruit, and one of them being cut and tasted, Mr. Wilmot pronounced it to be far superior in flavour to any queen pine that he had ever tasted at this season of the

year.

See Mr. Wilmot's letter, which forms the succeeding article.

3. A great saving of heat in the case of forcing all trees or plants which can be trained on walls or trellises, and in the case of ornamental stove trees or shrubs that can be so trained. The manner in which this can be effected is, by planting the trees against a perpendicular wall or trellis, or against a wall or trellis with any required degree of slope, and covering the wall or trellis with glass; the border having a vacuity underneath it, so as completely to isolate the roots, and admit, by the general arrangement already described, of a constant circulation of warm moist air between the glass and the wall, between the upper surface of the border and whatever covering may be placed over it, and underneath the border. In consequence of this arrangement, a very small volume of air requires to be heated, while the circulation of the air is more certain of passing through among the leaves, blossoms, and fruit. The border where this system is adopted may either be covered with a boarded roof at the distance of 1 or 2 feet from the soil, or with glass sashes at the same distance; and, in the latter case, the surface of the border may be used as the surface of a hot-bed, and pots of strawberries or other plants set on it to be forced, or sown or planted in it to be grown. The only disadvantage attending this arrangement is, that the trees trained against the wall can only be examined by persons outside the glass, and, consequently, that when they are to be watered or pruned the glass must be removed. Even in large houses or pits, where pots of strawberries or kidneybeans are placed immediately under the glass, only a stratum of 1 or 2 feet in depth will require to be heated; and, by arrangements, that object can easily be effected. For example, a temporary flooring of boards under the plants trained, or under the pots of strawberries or kidneybeans, with the joints made airtight by strips of paper or canvass glued on, would be sufficient. In some cases, a bed of earth, which might serve as the border for roots of vines or peaches, would render this temporary flooring of boards unnecessary.

4. All the plants, including cucumbers, which were in fruit, and some shrubs which were in flower, were in remarkably vigorous health ; so that the circulation of the air, independently of all other circumstances, seems to produce a positive benefit to the plants. The blossoms of the Persian lilac, when forcing, are generally without fragrance, but Mr. Wilmot and ourselves found that this was not the case here. In short, as Mr. Wilmot 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 according 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 temperature. 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 1819 in Colvill's Nursery, King's Road, and described in our Encyclopædia of Gardening, edit. 1835, p. 558. By means of such an apparatus, the forcing might go on for days together without any attention from the gardener, provided fuel and water were supplied to the boiler; and by a self-supplying hopper, and the use of coke or anthracite 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 thermometer 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 upright sashes placed in front of peach trees or vines, the hot-water pipes placed behind, and the hot air brought up as shown in fig. 21. Then, if the border were supported on flagstone, like that of Mr. Jedediah Strutt at Belper (see our volume for 1839, p. 448.), 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 potatoes planted, or cucumbers and other dwarf or spreading articles

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grown. In fig. 21. a is the front glass, nearly upright, and consequently well adapted for winter forcing, when the sun is low, and will strike it nearly at a right angle; 6 is the path of boards under which sea-kale, chiccory roots, &c., in pots might be forced; C, the horizontal glass over the border; and d, the gratings to the drains. The direction of the current of air is shown by the arrows. Fig. 22. shows part of the ground plan, in which e e are the

22 drains, f f the situation of the gratings, g the hotwater pipes, and h the airtube. A thermometer, and a hygrometer acting by gravity, might be hung inside the front glass, and inspected by walking along the boarded path. When pruning or watering was required, the warmest moments of a fine day should be chosen, and the sashes opened one by one for a few minutes. Fumigation by tobacco might be performed when necessary, by burning the tobacco over the hot-water pipes; and it is almost unnecessary to observe that the atmospheric moisture might be increased to any desirable extent, by throwing down water among these pipes, so as to cover the bottom of the drains.

To prove the rapidity of the circulation, it is only necessary to throw a piece of burning paper among the pipes, or a little rose water or fragrant oil over them, when in a few seconds the smoke or the fragrance will be perceived over the front path. To make this construction and arrangement economical, shutters of boards, or of hurdles covered with bark, reeds, or straw, should be adopted both for the front and horizontal glass.

About the end of the last century, an attempt was made in the neighbourhood of Bristol by Dr. Pritchard and others, and revived again by a Lincolnshire gentleman, to enclose a large space, cover it with glass, and heat the interior to the temperature of Madeira, as a substitute for that climate to invalids: the plan did

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not succeed, for want, among other causes, of efficient ventilation, combined with adequate heat; but by Mr. Penn's plan all difficulty on that point will be readily overcome. Suppose, however, that the plan had no other advantages than that of rendering the air of orchidaceous houses and stoves agreeable to the feelings, instead of being oppressive and unbearable; that result alone would be sufficient to constitute it one of the greatest improvements that have hitherto been inade in the production of artificial climates for plants.

In conclusion, we have only strongly to recommend all such persons as may be disposed to try Mr. Penn's plan, to apply to Mr. Penn himself; not only because he must necessarily understand his own plan better than any other person, but that, being an independent man, and most eager for the celebrity attendant on the dissemination of his plan, he is most likely to carry it into execution cheaper than any other tradesman can do. Indeed, Mr. Penn authorises us to state that he will carry his plan into execution any where in the United Kingdom; and, after a year's trial, if it should not give entire satisfaction, he will take the apparatus back again, and replace whatever apparatus may

have been there before, entirely at his own expense. We are the more particular in stating this, because, from the circumstance of Mr. Penn's not having taken out a patent, and the invention being likely to come into universal use, there will, as in the case of Arnott's stoves, be numbers of imitators, and pretenders to improvements, who do not understand even the first principles on which the arrangement acts.

With the most noble and disinterested views, and apparently, also, with views the most judicious with reference to the public good, Dr. Arnott left his improvement open to the competition of every ironmonger; in consequence of which, every ironmonger constructed Dr. Arnott's stoves, and by far the greater number of them spoiled them. It would have been much better for the public had the doctor taken out a patent. We wish Mr. Penn had done so; but, since he has not, we consider it our duty most strongly to warn the public against employing others to execute the plan of an inventor, when they can get it executed by the inventor himself, and that with the advantages above stated. We have only to add that Mr. Penn undertakes to construct all kinds of hot-houses, whether of timber, or of iron or other metal. - Bayswater, Feb. 8. 1840.

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Art. X. Mr. Wilmot's Opinion of Mr. Penn's Mode of heating and

ventilating Hot-houses. Communicated by Mr. Wilmot, F.H.S., &c.

As you have written to me on the subject of Mr. Penn's principle in heating hot-houses, pits, &c., and expressed a wish for my opinion thereon, I will endeavour to convey it in a few words.

About the middle of April last, Mr. Penn had twenty large pine plants from out of my houses, a number of which were queens; and it is universally acknowledged that at this season of the year the queen pine is of little value, in size, appearance, or flavour, rarely seen to swell the pips prominently, or to come of a good colour. The result of Mr. Penn's principle, in this instance, has fully confirmed my opinion that forcing is a farce without it. My pines, in the same pit from which Mr. Penn had his plants in April Jast, are now ripening, and some cut, swelled, as they usually are, to about a pound and a half each, and with a flavour little better than a Swedish turnip. Those at Mr. Penn's (one of which you and I partook of yesterday) possessed every property of a queen pine. It was well swelled, of a most beautiful colour; and its flavour was equal to any queen pine ripened in August. Mr. Penn's pretensions to horticulture are certainly very limited. He knows but little about forcing; the gardener that grew the plants, less. Such being the case, it can only be the system which has produced such an effect on the size and flavour of the pine. This system, I am happy to say, has far exceeded my most sanguine expectation, and as it must be seen, fully to appreciate its value, I shall be happy to exhibit it in action to the horticultural world about April next, when I shall invite all friends to horticulture to see it at work in

my

extensive forcing establishment. — Isleworth, Feb. 6. 1840.

P.S. The man that grew the pine plants having lately left Mr. Penn, I cannot accuse his present gardener of want of ability.

Art. XI. On the Conical Boiler for heating Hot-houses by hot Water.

By D. Beaton. If the reader will turn to the 13th volume of this Magazine, at page 298., he will find drawings and descriptions of the original conical boiler, which was invented in 1835, at New York, in the United States, by a lad only 18 years of age.

This useful invention, which is destined to make an entire revolution in the system of heating by hot water, created little interest at that time in Britain, and might have passed down the current of oblivion like the mere bubble of a season, had it not been for the ingenuity and perseverance of J. Rogers, Esq., F.H.S., Vine Cottage, Sevenoaks, Kent. Under this gentleman's directions

, it was greatly improved by Mr. Shewin, ironmonger, of the same place. The credit of bringing this boiler prominently before the British public is therefore due to Mr. Rogers.* He presented

Since Mr. Beaton sent us this article he has supplied us with the following note. “I have since learned that, as far as Mr. Rogers is concerned, it

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