PRACTICAL TREATISE ON THE CONSTRUCTION OP STOVES AND OTHER HORTICULTURAL BUILDINGS; and on the Principles of Heat AS APPLIED TO HOTHOUSES, CONSERVATORIES, GREENHOUSES, AND ALL OTHER HORTICULTURAL ERECTIONS, WITH USEFUL REMARKS AND SUGGESTIONS ON THE FLUID EMPLOYED AND THE APPARATUS BEST ADAPTED TO THEIR APPLICATIONS. Illustrated with twenty-six wood engravings By J. W. THOMPSON, NURSERYMAN, LANDSCAPE GARDENER, AND HOTHOUSE DESIGNER, NEAR BEULAH SPA, CROYDON, SURREY. Front view of Syon Conservatory, London: PUBLISHED BY R. GROOMBRIDGE, PANYER ALLEY, PATERNOSTER ROW. Price, 2s. 6d. R. Greenlaw, Printer, King's Cross, AMR. READ’S WATERING ENGINES. I annex the accompanying drawings with which I have been kindly favored by Mr. Read, for the use of this work.PRACTICAL TREATISE ON THE CONSTRUCTION OF STOVES AND OTHER HORTICULTURAL BUILDINGS, AND ON THE Principles of Heat AS APPLIED TO HOTHOUSES, CONSERVATORIES, GREENHOUSES, AND ALL OTHER HORTICULTURAL ERECTIONS WITH USEFUL REMARKS AND SUGGESTIONS ON THE FLUID EMPLOYED AND THE APPARATUS BEST ADAPTED TO THEIR APPLICATIONS. By J. W. THOMPSON, NURSERYMAN, LANDSCAPE GARDENER, AND HOTHOUSE DESIGNER, NEAR BEULAH SPA, CROYDON, SURREY. London: PRINTED BY R. GREENLAW, FOR THE AUTHOR, 40, CHICHESTER PLACE, KINGS CROSS. A 1838.A PRACTICAL TREATISE, &c. &c. Knowing that the materials generally used in the construction of all horticultural erections, viz., wood and cast iron, has been a controverted subject, and that a great diversity of opinion exists as to what description of materials are of most avail, it is my intention in this brief Treatise to point out, 1st, the advantages of wood over cast iron in the frame work, for all horticultural designs : 2dly, the superiority of hot water over heated air and steam as a medium for conveying genial heat to plants : 3dly, the consumption of fuel; 4thly, in time and labour of attendance: 5thly, the advantage gained by water heating more rapidly, and cooling more slowly than steam: 6thly, the superiority of the egg-shaped boiler. Directions to prevent disappointment in the use of the hot water apparatus, by preventing, first, the accumulation of air in the angles of the pipe, by taking care that the water in the boiler and the supply cistern shall not sink beneath the level of the top pipes: second, by allowing space for the expansion of the metal in the various places when the pipes have to pass through solid bodies of brick, stone, &cc., &c. Directions respecting the proper caliber of the conducting pipes, and of the boiler; warning against suffering the accumulation of calcarious or other deposits in the pipes, by the use of unclean water, with an analysis of five different kinds of water; (kindly favored by Mr. Budd, the chemist, for this publication ; see appendix;) caution against over confidence in this changeable climate, and against employing improper persons, i. e. non-practical men, to give designs for houses, &c. Necessary care should be taken to have a proper sized furnace door, and of the pipes when ascending and descending under door-ways, &c.; the effect of arid air, being detrimental; of humid air, beneficial to the health of plants; noxious gases evolved from heated air and steam, nutritious; gases evolved from hot water, kc., &c.Knowing that both gentlemen and gardeners are hourly subjected to much inconvenience from the bad situation and construction of their greenhouses and other horticultural buildings, as well as from the various modes of heating such erections, in consequence of no practical directions having been published for their assistance or guidance by men practically acquainted with the subject, and who, like Hercules, have actually put their shoulders to the wheel. I am induced, from having devoted several years to the subject now under consideration during my practice in her Majesty’s Botannic Garden, at Kew, and in several other departments of the Royal Gardens, as well as in many private establishments, where fruits and plants have been extensively and successfully cultivated, to offer for the assistance and consideration of all persons interested, a few practical remarks after the result of fifteen years observation and calculation, all of which have been' gleaned by dint of personal labor, during which time, I regret to say, that I have not only witnessed the destruction of fine crops of grapes, and other forced fruits, from badly designed houses, but also from the escape of smoke, of carbonated, hydrogen, and other destructive gases which are evolved from common flues when over heated, a circumstance that must always occur on cold nights in forcing, and in other glass-roofed houses where a large cooling or radiating surface, such as glass, is exposed to the action of the external atmosphere; the escape of these noxious gases is caused by the unequal expansion and contraction of the materials used in their construction, which leaves apertures between the joints of the bricks, and other parts of the flue. Moreover, it is a fact too well known to gardeners to require comment, that brick flues, after-having been in use for a few years, become very unsafe for early forcing when strong fires are applied, from their liability to burst. During my experience I have known several pine pits, as well as plants entirely destroyed, by this cause, from the leaves or tan with which the interior of the pits are filled, in contact with the sides of the flue being set on fire ; these misfortunes generally occur about midnight, or after the fires have been made up by the attendants, who are then enjoying repose from the toil of the day; and it is not only attended with a serious loss of property in the materials used in the erection, but also in the crop, which has been produced at a great expense to the proprietor, in cultivation, and a source of much anxiety and labor to the practicalgardener, who, for months, and perhaps years, has watched their progress and administered to their wants with the same watchful eye and unceasing care that a fond mother does to her helpless babe. An instance of the disastrous evil of the bursting of flues, and the great danger of magnificent mansions being destroyed by fire, from such melancholy accidents, is illustrated in the unfortunate destruction last winter at Sir James Sugden’s mansion, occasioned by the bursting of the flue of the conservatory, and I doubt not but most of my readers are aware this is not a solitary instance of valuable property being destroyed by similar causes, I could relate several others if necessary. It is therefore my intention in this brief Treatise, first, to point out the injurious consequences arising from badly constructed houses used for horticultural purposes, and of the injury and injustice done to gentlemen and gardeners, by employing non-practical men to decide on the locality for stoves, conservatories, greenhouses, and other similar erections; second, to offer a few observations (which are founded upon that never erring test, practical experience,) on the defects and advantages of the two materials generally used in their construction, namely, cast iron and wood; and lastly, to point out the respective merits and demerits of the three modes generally adopted for heating horticultural erections, (that is to say by common flues, steam, and hot-water) with some practical and highly important instructions to persons who have the management of hot-water apparatus, and who are unacquainted with the cause of their occasionally not acting properly with directions how to rectify this inconvenience without applying to engineers. The first, and most important object to be attended to before commencing any horticultural erections, is, to select a spot, where the sub-soil if not naturally dry, should be made so by draining off all stagnant water, so as to leave the foundation perfectly dry; second, the situation should be open and airy, and where the rays of the sun and light are not intercepted by tall trees, or any other body calculated to prevent the plants from receiving the full benefit and influence of the light and air. Neither is it absolutely necessary for conservatories, or greenhouses intended for the growth of such plants as are denominated greenhouse plants, to front the middle or meridian sun, unless the object is to have them in flower very early in the spring months, as I have proved during my experience that south -east, or south-west, arc points of the compass better adaptedfor the culture of greenhouse plants generally (or with very few exceptions,) than any other aspect, particularly when span-roofed houses are erected. Moreover, I invariably when local circumstances and situation will allow, place the two points so as to face east and west; see accompanying design, made by me for Mr. Perkins’s large greenhouse, which plan has also appeared in Mr. M‘Intosh’s work, the Flower Garden, from drawings lent by me for his use. See part V. of the Flower Garden, for July 1838. which is 66 feet long by 20 wide, heated with water. Fig. 1.—Elevation. Fig. 2.—Section. Fig. 3.—Ground Flan.in which work, lent by me for his use, are also to be seen an elevation, section, and ground plan of the magnificent conservatory of Lord Ashburton, at the Grange, Hampshire, one of his Lordship’s seats, see page 15.) But when situation and other causes make it necessary to have only one front, or what is technically called a lean-to-roof, I recommend a similar plan to the one here shown, of a stove that I made for H. Harvey, Esq., which is fifty feet long by Fig. 1.—Elevation. (Heated with hot-water.) Fig. 2.—End Section of Roof and Stage. sixteen wide, for growing hothouse plants on stages without bottom heat, with hollowed shelves so as to receive about one inch of sand to keep the bottoms of the pots always moist, which plan, if generally adopted with stove plants not plunged in bark beds, would be found very beneficial during the hot months of summer.But, although 1 have only given two designs for greenhouses and stoves in this brief Treatise, I beg to observe, that no erections offer greater facility for accommodating the various localities of gentlemen’s establishments, and of suiting the fancy and taste of the owner, than buildings of this description, which will admit of endless advantageous modifications, but of course it must be borne in mind* that in proportion to the convenience furnished to the practical gardener in the formation and elevation of the house, will be the degree of success to the employer in the culture of the crop. It must then be evident to both amateurs and gardeners who are acquainted with the subject, that a house intended for the growth of hard wooded and slow growing New Holland, and Cape of Good Hope plants, when the object is to cultivate large and lofty specimens to exhibit the plants by planting them out in beds in their natural state, would be the very worst construction for the growth of Geraniums, Calceolarias, and other similar succulent, wooded, and fast growing plants. Hence it is, that gentlemen’s gardeners who generally exhibit the latter description of plants, at the various horticultural meetings in the neighbourhood of London, and other places, are not able to compete with the celebrated hard-wooded and rare, delicate and choice species of plant growers in the neighbourhood of London, such as Mr. Lee of Hammersmith, Messrs. Lod-diges of Hackney, Mr. Low of Clapton, Mr. Knight of the Exotic Nursery, Mr. Rollinson of Tooting, Messrs. Young of Epsom, Mr. Pamplin, Messrs. Colville, now Derbin and Adams, Mr. Fairbairn of Clapham, Mr. Rogers, late Allen and Rogers of the King's Road, Mr. Henderson of the Edgeware Road, Messrs. Lucomb and Pince of Exeter, Messrs. Brown of Slough, and Piccadilly, all of whom are celebrated growers of the first description of plants alluded to. The cultivators of the beautiful hybrid new and rare varieties of Geraniums, &c. which constitute the second class of plants alluded to, are, Messrs. Colly and Hill of Hammersmith, Mr. Gains and Mr. Russell of Battersea, Mr. Groom of Walworth, Mr. Dennis of the King’s Road, Mr. Catcleugh, of Sloane Street, and Mr. Cock, Chiswick all of whom are noted cultivators and exhibitors of this description of plants in the highest state of perfection, and are equally as celebrated for the culture of the succulent fast growing varieties, as the first-men-tioned gentlemen are for the rare genera and species ; and the reason why the gentlemen's gardeners are unable to contend with the celebrated growers and exhibitors, does not arise as is erroneously and unjustly supposed from want of any attention or skill of the gardeners, or want of knowledge in the culture of plants, but from the inconvenient construction and elevation of the houses, and also from the immense quantity of plants, from which, they as men in business, have it in their power to select specimens for exhibition, unless in a few instances, when the proprietor becomes an amateur, feels an interest in the garden, and furnishes the practical man with the same facilities, as regards erections, &c. it will invariably be found that the gardener excells by far, and eclipses the nurserymen which is verified in several instances by the various gardeners who contribute plants to the Chiswick, and other horticultural exhibitions in the neighbourhood of London ; namely, Mr. Redding, gardener to Mrs. Maryatt of Wimbledon; Mr. Green, gardener to Sir Edmond Antrobus, Bart, of Cheam ; Mr Barns, gardener to Mr. Norman, of Bromley Common; Mr. Bannan, gardener to Jones Loyd, Esq. of Wickham Kent; Mr. Hunt, gardener to Miss Trail of Hay's Common ; Mr. Skerrett, gardener to Lord Farnborough of Bromley Hill; Mr. Falkener, gardener to II. Palmer, Esq. of Cheam; Mr. Ferguson, gardener to T. Labouche,Esq. of Highlands ; the gardeners of George Glenny, Esq. of Worton Lodge ; Mrs. Lawrence of Drayton Green ; S. Boyd, Esq. Bromley, and many other equally successful competitors, who it will be found generally carry off the most valuable prizes given for plants and other horticultural productions. These few demonstrated facts clearly prove the accuracy of my opinion relative to the construction of houses for the culture of plants, and the absurdity of any gardener attempting to vie with such exhibitors where he is limited to such means as most of the old plans of greenhouses afford, and even many of the modern ones, where the practical gardener has not been consulted in the erection are equally bad in the construction, and as ill adapted for the successful growth of greenhouse plants as many of the houses built a century ago. As all non-practical architects look to what they call ornamental architectural erections, by which arrangement, they not only cause a waste of property in their first erection, by having ridiculously lofty front glass, &c. &c. but they defeat the intended object of both the proprietor and cultivator, as it is utterly impossible for any gardener to grow neat and Rpretty bushy plants in lofty and dark-roofed houses, caused by the unnecessary depth and thickness of wood used in such unwieldy and unsightly erections ;* 1 therefore most strenuously advise, whenever buildings of this kind are projected, that the gardener be consulted as well as the builder, whose suggestions will be found equally valuable with the architects, and indeed the proprietor ultimately, in loss of property, suffers, when the pride of the artist forbids his consulting with these practical men, which I regret to say is too often the case ; and it is, as I repeat again, to the great detriment of the proprietor both in pocket and disappointment as regards horticultural productions, and floricultural displays; whenever it occurs in buildings for these purposes that the architect and gardener do not work mutually together, and are not equally interested in the success of the erections of their employer. A great difference of opinion prevails as to what description of materials for rafters, &c., are of most avail in the construction of roofs for stoves, greenhouses and other buildings intended for the culture of fruits and of tropical and other exotic plants; now, as I have had for years the management of the extensive ranges of glass at Syon House, as head gardener to the Duke of Northumberland, and at Kew gardens and other places, where the construction of the rafters, and such frames was both of cast iron and wood, I am induced to submit for consideration the result of my practical observations relative to the two descriptions of houses under remark, as a guide to persons intending to raise such erections, but who arc unacquainted with the injurious consequences of ill constructed hothouses, &c. intended for horticultural purposes. Having had fifteen years practical experience, and the management during that long period of above three thousand running feet of glass designed for the culture of fruits and plants, 1 am enabled to speak with some decision on the subject; and there are, I doubt not, hundreds of practical men who will confirm the truth of the following observations and agree with me in the decided conviction, I entertain of the superiority of wood over iron. I feel fully justified indeed in saying that when the respective merits of wood and demerits of iron, are fully ascertained, the numerous prejudices in favor of the latter will cease to exist in the minds of all candid men who are practically acquainted with the properties of the two materials. • Vide the plants in the dark-roofed Conservatory in Kensington Cardens.Every person possessing even a slight knowledge of the expansion and contraction of all metallic substances may form some idea of the injurious consequences of the expansion of a large iron-roofed house in a hot summer's day, and of its contraction during a night of severe frost. So powerful have I known the action of the sun’s rays in expanding the iron rafters and lights of a large iron roof on a hot day, that I have found the strength of three men insufficient to force down the sliding lights for the admission of air. In fully equal proportion have I witnessed the contraction of the metal during the intensity of winter, when so large have been the apertures between the rafters and lights, as to admit the external air in a degree sufficient to counteract entirely the power of two strong fires, (when the flues have been heated to the greatest extent) and to render a considerable time necessary to raise the temperature of the house to three degrees of Fahrenheit, the thermometer then standing at eighteen degrees of frost. This was in February 1830. Now this occurrence took place in a house of no very great extent when compared with the wood roofed houses I shall hereafter describe. Its dimensions were forty feet long by sixteen wide, and nine feet high, with a pit in the middle for the culture of pines, &c. which very much reduced the number of cubical feet of air to be rarefied, compared with the wood roofed house, which was fifty feet long, fourteen wide, and fourteen feet high, without any pit in the middle. Having stated the dimensions of the houses, I shall now give the result of the investigations and calculations relative to fuel, attention, &c. &c. &c. The coals for both houses were measured before being placed for use, and after the consumption of the night’s fuel, the result was as follows; the iron-roofed house with eighteen degrees of frost, required the consumption of nearly six bushels of coals, and almost unremitting attention during the night, or until three o’clock in the morning, while the house with the wooden roof consumed scarcely three bushels of fuel, in order to keep it at the same temperature as its iron rival, and 110 attention was required after ten or eleven o’clock at night, when the fires were made up and left. Not satisfied with this, but being determined to investigate thoroughly the merits of the two materials, in every point of view, I caused a house, constructed of wood, and also one of iron, both of precisely the same dimensions as regards the superficial feet of glass, to be perfectly repaired in the autumn of 1832. On having them examined and restored in the following season, I found that the cost of repairing the ironhouse, was nearly double the sum required to repair the house of wood. 1 do not mean to say, that double the number of squares were absolutely broken, but including the broken and cracked squares, there was more than double the number destroyed, and this I attributed to the expansion of the iron during summer, and its contraction during winter. From these calculations it is quite evident that wood has the advantage over iron in three very essential points, namely, saving of fuel, glass, and labor. With regard to the growth of plants and fruits, I have invariably found that plants do not thrive so well, nor look so healthy in an iron, as in a wood roofed house, the non-conducting power of wood, and the electrical, (may I say, calorific ?) sensibilities of iron, may be the cause of this difference ; iron is infinitely more liable than wood to the sudden and injurious extremes of temperature. I have always found, during my experience, that no matter how iron houses might be situated, unless there was a slight shading on the roofs during the hot days in summer, the leaves of the pines and other plants become very brown, and frequently scald, but whenever these shadings are not used, I would strongly recommend that a large cistern or troughs of water should be placed about the inside of the house to make up for the continued evaporation, and for the deficiency of moisture exhaled from the inside of the house by the powerful action of the sun on the glass, so as to keep up a natural humidity of the surrounding aqueous medium. One important circumstance which is worthy of the gardener’s attention is, that iron-roofed houses should be painted internally either annually, or biennially at the farthest, to prevent the drip from the corroded iron, injuring the foliage, for I have always found this oxyde, or metallic deposit, from the iron, injurious to the leaves of plants. After these remarks made on wood and iron, I continued my observations in the season of 1831 which fully confirmed the accuracy of my previous calculations. By working two houses at the same temperature, (fifty-five to sixty of Fahrenheit), the result was as follows, the wood-roofed house consumed only a bushel and a half, while the iron took from two bushels and three quarters to three bushels every night. This last experiment was made two months later in the season than when my attention was directed to the subject before, but then you will see it bears the same proportions as to fuel, &e. The dimensions of the houses were as follows, the wood-roofed fifty feet long, sixteen wide, and twelvefeet high ; the iron fifty long, sixteen wide, and twelve high ; the latter was a vinery, and had a pit in it for the culture of pines, which, as in the former experiment, very much reduced the number of cubic feet of air to be heated, as compared with the wood-roofed, which was intended for the culture of peaches, and had no pit in the centre. Notwithstanding, however, that the whole of my observations and calculations are unfavourable to iron roofs, 1 am willing to admit that for lightness and neatness of appearance in the structure, iron has, and will always have the advantage, it would be almost impossible without iron to erect such magnificent conservatories as those of the Duke of Northumberland at Syon House. Fig. 1.—Ground Plan of the Conservatory at Syon House, shewing the arrangement of the Steam Boilers, Pipes,&c.Fig. 1. Plan and elevation of the magnificent conservatory of His Grace the Duke of Northumberland at Syon House, shewing the arrangement of the plant houses, the boiler house, the steam boilers, and pipes for heating the various erections designed and executed by C. Fowler, Esq. The interior arrangement of the houses for the culture of the various genera and species of plants, was planned by His Grace as well as the design for the tasteful flower garden in front of the conservatory, which was also executed from His Grace’s own drawings. The entire length of the range of houses is nearly 600 feet; the centre represented by a glass dome,see fig. 2, is about 65 feet high, divided as follows: 1 Camellia house ; 2 Geraniums, and other plants of similar habit; 3 New Holland, and other hard wooded species; 4 For delicate stove plants grown in pots, and plunged in bark beds; 5,5,5 is a stove a hundred feet long for the growth of large trees such as cocoa nuts, and other lofty fast growing tropical plants, which are planted out in beds of properly prepared earth, and some of them are now nearly forty feet high, particularly the Elate palm, presented to His Grace by Lord Tankerville, about six years ago; 6 For delicate stove plants grown in pots, and plunged in bark beds; 7 For a choice collection of heaths, and other hard wooded Cape plants; 8 For a miscellaneous collection; 9 The Orange house ; A A vapor valve for steaming the houses ; BB. CC. similar but smaller valves for the same purpose; the centre division has seventeen four-inch cast iron pipes below the paths, all round the four sides of the division. The steam enters from the main at D, and the condensed water passes off at E. The two square divisions adjoining the centre one have fourteen four-inch pipes round three sides each. The steam enters at F. F. and the condensed water passes off at G. G. The first curved division on either side of the centre has six pipes each at the front, and six at the back. The steam at the main enters then at II. II. The other curved divisions have five pipes in the front and four at the back of each division; the condensed water escapes at 1.1.1.1.1.1., the end divisions forming the extreme wings of the range, have eight pipes, all round, branching each way from the end of the main at at K.K. and deliver the condensed water at L.L. M. pipe for warming the back sheds. N. main entering propagating pipes; condensed water passes off at O. P. chimney divided into four, these to cut the column of smoke ; Q. the two steam boilers for heating the houses; R. the boilerhouse; S. coal sheds; T. potting sheds ; U. four propagating or nursing pits; V. the main steam pipe from the boilers enveloped in saw dust, a non-conductor of heat; while passing along a hollow wall into the culvert, and entering the range at the centre or domed house; W terrace walk. I forgot to mention when speaking of Mr. Fowler, as the architect employed by His Grace in the improvements made in the gardens at Syon House, that he was also the archtiect engaged by His Grace the Duke of Bedford for re-building Co vent Garden market, likewise the designer of Hungerford market. Fig. 2.—Elevation of Syon Conservatory. At the end of the middle walk of the botanic garden as shewn in the annexed perspective view of the range of houses, is placed a large ornamental basin and fountain, supplied from a pure spring, which rises about a mile and a half from the garden. At the back of the propagating house as shown in the ground plan, fig 1. is a row of sheds, the entire length of the propagating erections, which are heated by a steam pipe, and used for potting of plants during the cold winter and spring months. Having now given a brief description of the conservatory and botanical department of His Grace’s garden establishment, I shall now furnish my readers with a plan of the ranges of glass in the kitchen garden, the entire length of which erections, including the pits for succession pines, and small houses used for forcing American plants, roses, lilacs, and other shrubs generally forced for cut flowers, is about a thousand feet in length.Fig. 1, represent* the elevation and end sections of the principal ranges of glass in the kitchen garden at Syon, which is 400 feet long and heated with hot water divided in the following manner, Nos. 1, ‘2,3, 9, 10, 11, are used as fruiting pine house*, Nos. 4, and 8, are peach houses, and 5, 0, and 7, are vineries, and in each of the other houses with the exception of the two peach houses, vines are introduced, but are trained under, the rafters only, and not more than one rod or shoot allowed to be trained up each. The brick building shown in middle of the range is the residence of the foreman of the botanic garden, the kitchen garden, and melon ground, and is of sufficient size to accommodate six journeymen gardeners, and by the kind arrangement of His Grace himself in this department, they enjoy every domestic comfort. 1 his humane consideration reflects the greatest credit on His Grace, and his example may stimulate others to contribute more to the common necessaries of the journeymen gardeners than is generally attended to in gentlemen’s garden establishments, for with the philanthropy so characteristic of His Grace’s munificent disposition, he has most laudably studied to add to the comforts of every man employed in the gardens, and indeed, his benevolence is extended to every individual whom he employs. At the back of the principal range, in a line with the men’s apartments is a row of sheds from twelve to sixteen feet wide, the entire length of the range of glass, subdivided into compartments for garden tools, mushroom houses, packing-sheds, fruit rooms, and places for keeping tan dry, so as to be ready for use when wanted, also a boiler for the purpose of steaming the forcing houses, as it is technically termed. Fig. 2 is a plan of the range of pits used for succession pine plants, &c. they are eight in number, divided into fifty feet lengths, by ten wide, and are appropriated as follows, Nos. 1, 2,3,4, each fitly feet in length, are for succession pines, 5 for forcing potatoes, 6 for early cucumbers, 7 for melons, 8 for French beans, rhubarb, and various other vegetables. Fig. 3 represents a range of small houses with a back walk covered with slates, for forcing American plants, pinks, roses, lilacs, and other forced flowers, &c. &c. they are divided into compartments, and are altogether about 120 feet in length, the other two pits are each about 100 feet long, for the culture of strawberries, which are forced to a very great extent, amounting to about 10,000 pots annually. I omitted to state when speakingof the principal range of glass, (see fig. 1) that in the six fruiting pine houses, there are shelves and boxes placet! along the back and other convenient situations for the forcing of French beans, cucumbers, kc. The following engraving is an elevation of the unique conservatory of Lord Ashburton, at the Grange in Hampshire. See the drawings, lent by me to the editor of the Flower Garden,— “The dimensions of this conservatory are eighty feet in length, Fig. 1.—Front Elevation. forty six wide, and twenty-one high, and was designed and. executed by C. R, Cockerell, Esq. The situation of this spacious area is adjoining that portion of the house dedicated to the ladies, the windows of whose apartments are directed towards the conservatory. This house, in regard to architectural and horticutural proportions, two important points in similar struc- Fig. 2. - A view of the interior arrangement of the Grange Conservatory.tures, but seldom agreeing together, or with a due regard to the various bearings of situation and circumstances, is, in my opinion, the most complete thing of the kind that 1 have seen either in this country or on the continent. A glance at the annexed diagram, which represents the section of the above splendid house, will at once show how easy it would be, where expense is a secondary consideration, to vary the the plan of a greenhouse or conservatory according to the ex- F»g. S.—Section of Roof, &c. tent of ground, and to have an exotic garden in which perpetual spring could be maintained. The roof, which in this example, is double, and which might be continued to any extent, is supported by cast iron hollow columns, a a, which also carry off the water that falls on the roof, into drains, properly placed for its reception, as at g, and which, after supplying an immense reservoir under ground for the supply of the house, as well as for use in the event of lire, or any other scarcity of water, empties the remainder beyond the limits of the building. These buildings are highly ornamented with mouldings, and have wires fastened to them at c, for the purpose of training creeping plants up them. The back and front walks ee, are four feet nine inches broad, and the centre and principal one c, six feet and a half. These walks are covered with an arched roof, formed of double plates of rolled iron fff, between which is left a space of two inches, which confines a stratum of air, to prevent the escape ofheat, or the admission of cold. Over these plates arc placed an iron grating for a safe walk, to enable the operatives to repair the glass, give air, &c. This house was heated by Mr. Sylvester, with steam, the pipes being placed under the walks, as at bbb Fi^. 4.-—Pari of Section. and the cavity aa, served as a reservoir for containing heated air, which was admitted into the house as required. The two steam boilers, were removed, about seven years ago, in consequence of the great quantity of fuel consumed to generate sufficient steam to heat the conservatory; it is now heated with hot water, In such extensive erections as those at Syon House and the Grange, iron is indispensable, and at Bretton Hall, Yorkshire, the seat of T. W. Beaumont, Esq. also the splendid structures for plants at Alton Towers, the princely residence of the Earl of Shrewsbury, which are only now eclipsed by Syon: and that r,ow erecting by the Duke of Devonshire at Chatsworth, which, when finished, will surpass every thing of the kind in the known world. In such stupendous structures, without the introduction of iron for rafters, columns, and other supporters, as the depth and thickness of wood ratters, &c. necessary in such buildings would give the erections a very dark, gloomy, and heavy appearance; but then much of that evil which I complainof arising from iron, might be obviated by having the sides of the lights made of wood, and the sash bars of copper, with small rollers affixed to the underside of the lights to make them run easy, but under no pretence should iron be used for forcing houses in pits, nor for small greenhouses or conservatories. I may, indeed, repeat that the use of cast iron for horticultural buildings, can only be justified in such extreme cases as those 1 have alluded to. I feel fully confident that if proper attention were paid to the construction of hot houses, and the materials used in their erection, the appearance of a wood-roofed house would not be altogether objectionable. For the assistance of persons building houses for horticultural purposes, who may have had less practical experience than myself, I will proceed here to give a brief description of such materials, and modes of construction as 1 think will combine the whole of the desired objects The first thing to be attended to is, to give the roof a proper pitch or inclination, so as effectually to carry off the water and prevent the drip in the house, which is highly injurious to plants grown in pots; Secondly, to form the roof in the following manner; the rafters to be of wood, varying according to the length of the roof from five to eleven inches deep, the section of it to be wedge-shaped from three to four inches in the upper, and about half an inch wide on the under side, the ends and sides of the lights to be made of wood, the top from four to five inches, the sides two inches and a quarter, and the bottom from six to seven inches wide. The sash bars to prevent as much as possible the obstruction of the sun's rays, should be of copper, which will give >he house a light and neat appearance, and yet not subject the plants to the injurious extremes of temperature, as the small quantity of metal in the thin sash bars, which need not be more than half an inch wide and about the same depth, will cause but very little variation in the temperature by radiation, and suffer little from expansion and contraction. Neither would it increase the expense of the light in any great degree over one made of wood; for as copper of those dimensions would not weigh more than six or eight ounces to the lineal or running foot, I should suppose it would be bought for about Is. 6d. per lb., the expense, therefore, would be trifling when compared with the advantages ; indeed, the extra expence would be repaid in a few years by the saving of wood in repairing the lights, as glaziers cannot hack out old putty without destroying the sash# bars, and this being frequentlydone, as is necessary when lights are kept constantly in use, very soon lessens the substance. I therefore recommend all persons when erecting forcing and other houses to have them constructed of the above materials, particularly if they are desirous of excelling in the culture of fruits and plants, as by the use of copper sash bars, they obtain all the desired objects, namely, lightness of appearance, economy of fuel, glass, and labor. I would further suggest that every gentlemen before erecting,or deciding on any particular plan or dimensions for a house or houses for horticultural purposes, should consult his own gardener, or some other practical man acquainted with the subject, as it is impossible for any architect or surveyor, unless directed by, and in conjunction with, the experienced gardener, to know the proper dimensions and elevations of a hot house to answer all the purposes to which it is appropriated so well as the gardener. It is true that an architect may make a very interesting external drawing, which to the eye, appears perfection, but which will, perhaps, never answer any one of the desired ends. Convenience as regards walks or paths, bark or tan beds, stages, flues, (or other modes of heating) cisterns for water, ventilation, and innumerable other little requisites and necessaries for a stove, greenhouse, or conservatory, may be overlooked in a design by one not intimately acquainted with the subject. Every gentleman who goes to the expense of erections of this description, expects in due time to have a return for his outlay in fruit, or the satisfaction of extraordinary fine individual specimens, in a general display of flowers. Should he eventually be disappointed in these anticipated gratifications, through the bad construction of his house or houses ; 1 regret to say it too frequently occurs that the fault is thrown on the persevering and anxious gardener who is consequently blamed for neglect of duty or want of skill, not only by his employer, but by others equally unacquainted with the cause. Upon examination of the house, however, by a competent and practical man, it generally turns out that the blame and ill success are attributable to its formation and aspect: various genera and species of plants require peculiar treatment and various situations, so that had the gardener been consulted as to the height of the stages, depth and width of tan beds, and proper situation for the flues, (or other modes of heating) all this disappointment to the employer and the employed would have been prevented. Moreover it too frequently happens with thesepretty plans prepared by non-practical men, that there is an insufficiency of means provided for the proper admission of air for stoves, greenhouses, inc. Want of attention to ventilation where the roofs are curvilinear, and constructed of iron is frequently attended with the most disastrous consequences. As a confirmation of the correctness of my observation, on the importance of proper ventilation, and as proof that plants are always liable to be scorched under a similar roofed house, I may state that I witnessed last summer the destruction of the whole of a fine crop of grapes, when nearly full swoln, as well as the foliage in a gentleman's hot house in Kent, which had been erected about five years. The destruction occurred through the architect failing to allow proper ventilation, and to prevent the second house of grapes, which had then suffered severely, from sharing the same accident, the gardener who is admitted to be as good a practical man as any in the kingdom, caused some holes to be made in the back wall of the house, about one foot wide and three long, where he introduced shutters hung on hinges, by which means he fortunately succeeded in saving the second house of fruit, but not without great injury to the foliage. This circumstance was generally known in the neighbourhood of Seven Oaks, and observed by many practical gardeners, who can vouch for the accuracy of this statement. Mr. M'Intosh, head gardener to the King of the Belgians and author of ‘‘ The Greenhouse and Flower Garden,” in Part X. of that useful little publication, published in March last, after detailing the results of his own experience of thirty years, further observes, “We avail ourselves of Mr. Thompson’s opinion, because he had ample opportunities of drawing unprejudiced conclusions, during the period he had the direction of the extensive ranges of hothouses, conservatories, &c. at Syon House, which have been considered the perfection of metallic houses. To his testimony he states we might add that of many others of equal credit, but we shall conclude by referring the reader to the opinions of Mr. Paxton, gardener to the duke of Devonshire ; Mr. M‘Muntrie, gardener to Lord Anson of Shughborough, and Mr. Thompson, late gardener to the Duke of Portland at Wel-beck, published in the Transactions of the Horticultural Society and Horticultural Register.” Having, I think, fully shown the advantages of wood over cast iron in four very essential points, the better growth of plants, the saving of fuel, glass, and labor; shall now offer a few practical observations on the various sys-tern* of heating houses as a guide for persons having the management of such erections. My calculations, I can assure my readers, are founded not on the false basis of theory, but on that never erring, and surest of all tests, practical experience, acquired only by the dint of much sacrifice of time, See. the various systems of heating houses, to winch I allude, areas follows; by common brick flues steam, and the circumvolution of hot water; the last named method is now becoming very general, and is admitted by all scientific men to be the best; because it is the safest, the most certain, and no doubt, the most economical as it regards the expenditure of fuel and the application of labour-Therefore, before entering on this important subject, I shall confine my observations in the first place to the advantages of hot water over steam for conveying genial heat to stoves, greenhouses, &c. which are in my opinion, many, and very great, particularly when coals are expensive; for to generate steam an enormous consumption of coals or oven coke (which is nearly as expensive) is indispensably required as a weaker fuel, will be found of no avail, when water is required to boil quickly. This is the first evil of the steam system ; and the second is, that a mail's time must be nearly, if not wholly employed in affording that constant attention which is necessary to keep up the fire. In the third place, there is a considerable loss of time, and not only time but fuel also before the pipes become filled with steam. This is a very important fact, to which, perhaps, due attention has not been paid, for it may not be generally known that steam travels through the pipes in a time no shorter than it requires to make them nearly as hot as itself. Steam, the instant that it comes in contact with a body colder than itself, becomes condensed, and its onward motion is of course impeded. Again, the moment the fire becomes too weak to keep the water at the boiling point, so that steam may be generated, it immediately ceases to furnish heat to the pipes, consequently they soon become cold, and this is the fourth evil of heating by steam; lastly, there is always great danger attending the system of heating by steam, when boilers have been in use for a few years, arising from their liability to burst, particularly where great attention is not constantly paid to the keeping of the safety valve clean and in proper order, so that nothing should impede its acting, when the pressure of the steam increases beyond its general power. Moreover, it should be borne in mind how much greater will be the expense in the first outlay in the erection of a steam apparatus, and from its beingmore complex than any other plan of heating greenhouses, &c.it is also attended with greater inconvenience and trouble to the gardener, from the circumstance of men as improvers in gentlemen’s gardens, frequently changing their situation for the sake of improvement, and of course, until another is initiated into the management, the gardener ought to attend to it himself. But all this danger, trouble, and ex pence are avoided by using a properly constructed hot water apparatus, for the instant the fire is ignited and the water gets warm, the particles of the fluid are set inmotion and circulation commences. This is caused by the rarefaction or expansion of a given bulk of confined water, from the temperature of 50 to 212 degrees; and, also, by the unequal weight or pressure of the two columns of water in the flow and return pipes, which being unequal in temperature, must be so in weight; therefore, the hottest water which is always in the flow-pipes, is naturally the lightest, and is kept in a state of circumvolution until both columns of water are equal in temperature and density, which cannot take place until the whole of the fuel is consumed, or so long as there remains a heat greater than that of the water itself in the furnace, in the bricks, or in the boiler. This is my opinion of the cause of the circulation of hot water through the pipes; therefore those boilers that present the greatest surface to the action of the fire (which is the great secret in all plans of hot water apparatuses) so as to keep up a continuance of the inequality of temperature in the two columns of water for the longest period, will be always found the most efficient and economical as regards fuel, &c. For in proportion to the rapidity with which the water that is continually returning at the bottom of the boiler, is rarefied or made lighter than that immediately behind it in the return pipe, so will be the velocity of the circulation of hot water through the pipes: and as the water both in the boiler and pipes is continually receiving a fresh supply of heat or caloric from the furnace, the same degree of temperature cannot take place in the water so long as the heat in the boiler, furnace, or bricks, is above the temperature of the air of the house through which the pipes pass. Now, as the air of stoves is generally, at least by night, 130 degrees below the heat of the hot water pipes, there must be a very rapid radiation or abstraction of heat from the iron pipes, in their passing through an atmosphere of a considerably lower temperature than themselves; which abstraction tends to keep up that perpetual circulation and regular supply of genial heat, whichis admitted by all practical men to be so conducive to the growth of plants. Still further, I have proved that two pipes, each four inches in diameter, the one filled with water at a heat of 200 degrees, and the other with steam, the pipe which contains hot water would sustain a much more enduring body of heat than that filled with vapour, and 1 have no doubt that when both pipes are heated up to the stated temperature, if the fires were allowed to expire, the pipe containing steam would cool as much in one hour as the hot water pipe would in six or seven hours. These are facts stated from accurate observations frequently repeated, and from exact calculations very severely tested, they may therefore be considered to demonstrate in the last place the decided advantages which the plan of heating by the circumvolution of hot water possesses over the system of heating by the diffusion of vapour. To the superiority of the hot water plan as to economy, both of fuel and labour, I may be allowed to bear witness, for during the last fifteen years, I have devoted the best energies of my life to the subject. Throughout that long period I worked four steam boilers, and had under my own eye the direction and application, of no less than six of the most approved systems for raising temperature by the means of hot water. This extensive experience, and the opportunities it afforded me of forming an impartial judgment on the merits and defects of all the different systems, added to a natural taste for, and love of experiment directed me to the construction of my economic oval-shaped wrought iron boiler, which has not only received the direct approbation of every engineer who has witnessed its operation, but is considered by them, and by all who have adopted it, as the most simple and economical of all the plans yet submitted to the public. The principal merit of the invention consists in the great surface the boiler presents to the action of the fire, and the introduction of a check draft and flange filled with water to divide the flues, instead of covering them with bricks, according to the general plan of boilers and modes of fixing, coupled with the simplicity of its construction ; and so confident am I of its superiority, that I always offer a guarantee to all who may employ me to fix it, that I will keep it in repair, and take the responsibility of its acting properly for three or more years,provided that it is fairly used. On such conditions those who favour my invention cannot run muchrisk nor entertain any apprehensions as to its efficacy; for, surely three years will afford them ample time to decide upon its merits and advantages; the chief feature of its arrangement being expanse of surface, and economy in fuel, &o. Another great object is the saving of caloric, as every person who is acquainted with the subject is aware of the tendency all rarefied bodies have to ascend, therefore, of course the top will be the hottest part of the flue. This oversight in most plans of hot water apparatuses caused me to direct my attention to the construction of a boiler that would retain the heated gases about the apparatus for a long period, and would be advantageous for the economising of fuel, as it always occurred to me, when considering the subject of heating horticultural buildings, that any means devised for the reduction of the consumption of so important an article of commerce as coal, (particularly during severe winters, when our rivers and canals are unnavigable) would be not only an individual but a national benefit; for by lessening the demand, we consequently cau3C a reduction in price in severe weather Moreover, I am of opinion, that by most of the present plans in use, of boilers, and the modes of fixing, that one third or more of the heat from the fuel escapes and is carried up the chimney by the admission of the quantity of air, necessary to support the combustion of the fuel, which saving I considered, could only be accomplished by confining for a longer period the heat, generated, about the boiler and preventing it from entering the chimney, until reduced to a temperature of boiling water, or to not more than 230 or 250 degrees of Fahrenheit; for, it must be evident to every person acquainted with the subject, that if the smoke and other gases liberated from combustion of the fuel be allowed to pass off into the air, at a much greater temperature than 220 or 230, there must be a great waste of caloric or heat. If it were even possible for the smoke, &c. to be reduced to a lower degree of heat when leaving the apparatus for the chimney, than that of the water in the boiler, that would also be a very injudicious arrangement and cause a waste of fuel, as smoke passing over the boiler, at a lower degree than the temperature of the water itself would abstract heat, rather than add it to the fluid. Another very important thing connected with this plan, is, that it acts as an apparatus for consuming smoke, which is always considered a very great nuisance about a gentleman's establishment, for when the carbonizing plate of iron which is placed on a slight inclination between the double doors of the furnace bars, becomeshot, nearly the whole of the carburretted hydrogen is consumed in passing over the heated body of coal or coke, by which means, that which is considered so great a nuisance, namely, the smoke which is evolved from the fresh supply of fuel, if thrown, a* it should invariably be done, after the fire is properly ignited on the carbonizing plate of iron, is turned to account in heating the water, rather than being wasted by its immediate escape up the chimney into the air, to the annoyance of man and injury of plants, but the plan of the apparatus, will be better understood by the annexed figures. Fig I. represents the front elevation. Fig. 2. represents a transverse section across the boiler and furnace, A being the furnace in which the fuel is placed, which is entirely surrounded with the boiler, except on the under side. B, is a check draft, over which the heat, flame, and smoke pass to a FIGURE I. Front Elevation. small aperture C, in the back of the boilers, which is represented in fig. S. communicating with the flues DD, which surround the lower part; these flues D D, unite and pass through an opening (E, fig. 1.) in the flange, over the furnace door to the flue F F, represented in fig. 8; this flue surrounds the upper part and terminates at the brick flue G, which is furnished with a damper to regulate the draft, and there will scarcely be a particle of heat lost by continuing this flue to the most distant part of the building. The boiler H in fig. 4, is in the form of an egg. It is represented in the plan with a chamber all round, connected with the check draft B, and surrounded with the flange 1, fig. 1. which divides the upper and lower flues. K is a cylindrical chamber on the top of the boiler on which, is the iron cap I. fig 1, either fixed or moveable, as may be required ; M M are the two outlet pipes communicating with the upper part of the boiler, through which the29 FIGURE II. Transverse Section. hot water circulates. After passing to the outside of the brick work, the pipes are ramified into as many branches as may be required ; N N are the two return pipes which enter the lower part of the boiler; O is the ash pit, with FIGURE III. Longitudinal Section.a door Q, to regulate the draft. The furnace Las double doors F, to exclude the external air. FIGURE IV. Ground Plan of the Furnace and Boiler. Fig. 5. represents the section of an oval boiler for large buildings with an additional or double chamber, surrounding the boiler ; this is only two feet FIGURE Vin diamater across the bottom, in the clear of the brick work, three feet six inches lone and two feet six inches high. During each winter I have made use of this boiler, with which I heated four hundred and forty-eight feet of three and four inch pipe, which warmed two large greenhouses, sixty feet by sixteen, and sixty feet by fourteen together with two pits, sixty feet by eight, and sixty feet by six. The author of the Greenhouse and Flower Garden in the Number for last March, speaking of the various plans of boilers recommended by Mr. Tred-gold, and other eminent Engineers, in their treatises on the various modes of heating, concludes, by stating, “ the only other improvements in heating, to which we shall now call attention, is a boiler invented by Mr. Thompson, near Beaulah Spa.” The editor of the Civil Engineer, in the 2d Number of that valuable work, published last February, states this Boiler to be “the most economical yet made.” See also an account of them in the Mechanics Magazine, the last week in February ; Marnock’s Floricultural Magazine, and Paxton's Mazagine of Botany, Harrison's Floricultural Cabinet, Macintosh's Flower Garden, for March and two following months. Figures 1, 2, 3, and 4, are intended for houses of small dimensions, and the larger one, figure 5, for extensive houses, this as well as the other boiler is oval shaped, and would be sufficient to heat 6 or 700 feet of four inch pipe at a trifling expense ; for, during the severest part of last winter, all the houses I have heated with this plan of boiler were kept up to their respective temperatures without burning one bushel of coals, the only fuel used was small coke, and during the intense frost of Friday night, January 19th, 1838, when the thermometer stood at quarter past six o’clock in the morning at 12 degrees below zero, or 42 degrees of frost, we had not the least difficulty in keeping every house both stoves and greenhouses at their proper temperatures. This statement of the extreme degree of frost, on the night alluded to at Norwood, I am induced to give, thinking, it may be interesting to some of my readers, and it may be relied on with much certainty, as I sat up the whole of that night as well as several others during the two last winters, to complete and prove my experiments on the cooling surface of glass, and heating surface such as steam, hot-water, brick flues, &c. As the night of the 17th and 19th January, 1838, were nights of the severest frost ever remembered in England, it afforded me a most advantageous opportunity of ascertaining very correctly the proper quantity of hot water pipe necessary to command any given degree of temperature required for stoves, greenhouses, and other buildings containing any specified number of superficial feet of cooling surfaces, such as glass, &c. which calculations I consider will be of great service to me in all my arrangements with hot water, as I have now most correctly ascertainedthe necessary quantity of pipe required, in all extremes of weather, even should the thermometer sink again to 12 degrees or more below zero. The want of which important calculations has been attended with the most serious destruction of property in many gentlemen’s gardens last winter, when water has been applied to heating such structures. As a proof of the importance of having a proper data for calculations of this kind in all arrangements for heating with water, I will just state a circumstance that came under my observation last winter, where the whole of a gentleman’s pine-pits, vineries, greenhouses, and conservatories, which are on an extensive scale, and are heated by three of the most approved plans of hot water entirely failed, in keeping the houses at the required temperatures, and where 65 degrees of heat was necessary for the vines and pines not more than 48 and 50 could be maintained, and in his conservatory and greenhouse, the gentleman sustained very considerable loss among his valuable collection of plants from being unable to command sufficient heat to subdue the frost. No doubt there are innumerable instances of the loss of valuable plants from the severity of last winter through an insufficiency of means not being furnished to the practical gardener, for the protection of such perishable property as exotic plants. But should any hothouse fixer feel inclined to devote a few nights during cold weather in some gentlemen’s gardens or nursery, where there are extensive ranges of glass, to these absolutely necessary calculations on the two radiating surfaces, namely, glass and hot water pipes, his calculations must not rest on the remarks made on a calm night of severe frost, unaccompanied with wind, for I have proved, as I before observed, by sitting up for whole nights together to attend to hothouses, &c. that frost of 42 degrees on the 19th of January, was not so trying to houses as 18 degrees of frost, accompanied with a strong wind; as a proof of which, 1 remarked, that in each of my six greenhouses and stoves, I failed in keeping them as hot by 5 degrees of Fahrenheit on the Wednesday night previous to the severe frost, when we had only 18 degrees of frost, which was accompanied with a strong east wind. The want of this practical and truly useful observations by all hot water fixers has been, in my opinion, the cause of so many complaints against this system for raising that temperature. This statement of the extreme degree of cold on the night alluded to has been mostcorrectly verified, by observations made at other nurseries and gentlemen s gardens. I will, therefore, give the names of a few places where the observations were made:—at Mr. Perkins’,Chip-stead, Kent, distant from London about 20 miles, they had 40 degrees ; at Col. Stables’, Streatham, distant from London 6 miles, 42 degrees; at Mr. Young’s Nursery, Epsom, distant 18 miles from London, they observed 40 degrees; at Messrs Rollinson’s Nursery, Tooting, distant 7 miles from London, 40 degrees; at Mordon, distant from London, 8 miles, they marked 44 degrees ; see observations in Gardener's Gazette. The last intense degree of cold, at Mordon, I should suppose can only be accounted for, from the low and damp situation, as the neighbourhood of Tooting, Merton, and the adjoining places are very low and marshy. 1 am aware that any information from practical men explanatory of the cause of improper working in so many hot-water apparatuses, will be acceptable to all gardeners, and other persons who have the management of them. I will, therefore, briefly state a few of the principal causes to which failures are attributable ; none of which are more difficult to overcome by persons unacquainted with the hydrodynamic principles on which the action of hot-water is regulated, than the accumulation of air in the pipes. Indeed unless proper arrangements are made for the escape of the air which is evolved from the water when heated, no apparatus can act properly; now, from some accidental cause, even in the best constructed apparatus, this air may collect and lodge in the corners or angles of the pipes, particularly when they have to rise and fall; this should be carefully attended to as the want of due regard to necessary precaution in this particular, is in my opinion, the principal cause of the many failures with hot-water; and the reason why this description of apparatus is sometimes spoken of unfavorably. I have invariably found from practical experience that water will not circulate beyond the point where there is an accumulation of air, the more powerful the at-temps made to remove the obstruction by increasing the strength of the fire, the more likely is the apparatus to work improperly, and to cause an overflow of water in the supply cistern; therefore as soon as it is discovered by the gardener or person having the management of the fire, that the water does not circulate regularly, he should trace the water by its warmth along the pipe to the place where he finds the metal cold, and then in the next angle, should he not find an air-tap, I would recommend him to procure a blacksmith’s drill, and have a hole made in the pipe, when Ehe will find the air pass off rapidly, and the water to follow instantly: then, should he not be prepared with an air pipe, a small wooden plug will suffice, until an opportunity offers to fix a pipe properly, as in all probability it might be many months and perhaps years, if the cistern be carefully and continually attended to, before such an accident would occur again at that particular joint or bend. I would however strongly recommend that in every apparatus ample provision should be made for the escape of the air at every bend where it is likely to collect or lodge ; for I have witnessed during my practical experience with several good plans of hot-water, that from some unknown cause, an apparatus which had worked properly for one or two years would suddenly get out of order; when, on tracing the pipe as before described as far as I found it warm, I have then, on drilling a hole, at the first turn beyond where the pipes began to feel cold, found an accumulation of hydrogen and carbonic acid gas, the heaviest of all the gases lodged in the angle, and as soon as this was allowed to escape the apparatus worked as well as ever. To remove this difficulty which to persons unacquainted with the cause of the obstruction would appear formidable, nay, almost insurmountable, not more than ten minutes was sacrificed; and on interrogating the man who had the management of the apparatus as to his care of the water in the cistern, I discovered that the derangement had been caused through his negligence and inattention, in having suffered the water to sink below the level of the top pipes, which of course left a vaccuum for this foul air to collect in. I would therefore advise that when the apparatus is not in use, the manager should either draw off the water, or keep the supply cistern as full as when in use; this precaution would prevent the air from collecting, but when the boiler is filled again, care should be taken to leave the air taps open until the water begins to flow out, or till the boiler is full, to prevent a repetition of the inconvenience. There is also .another highly important arrangement, connected with the hot-water apparatus, a property of the metals which should be attended to with great care, I mean the allowing of sufficient longitudinal expansion, for the pipes on their becoming hot, as it should be borne in mind that iron pipes when heated to two-hundred degrees, will expand nearly two inches in a length of one hundred feet; as a proof of the necessity for attending to this fact, I may relate a circumstance that fell under myown observation. A few years ago a nobleman's conservatory in Hampshire, was heated with hot-water at an expense of about three-hundred pounds; and the pipes from the boiler were introduced through the stone that formed the foot path, in which holes were cut large enough to admit a four-inch pipe, but not of sufficient diameter to allow for the expansion of metal; and I well remember, that, in consequence of this oversight in fourteen or fifteen different situations where the pipes had to pass through the stone, they burst; and in each of the eighty-feet lengths of pipe, which amounted to seven or eight lengths altogether, one third of their joints were destroyed after they had been used only three or four times. The same mischief, has, at intervals occurred to this hour, and will do so until room is allowed for the expansion of the pipes when they pass through the stone. The conservatory alluded to was the largest in the kingdom, until eclipsed by the one erected by the Duke of Northumberland, at Sion House, and was first heated at an enormous expense by two steam boilers, which were removed about six years ago, (after having been in use for about five years,) in consequence of their consuming a great quantity of coal and apprehensions being entertained of their bursting from the unsound state of the boilers. Having thus given a few brief instructions for the management of hot-water apparatus, and knowing there exists a great diversity of opinion relative to the quantity of water a boiler should contain, and of the dimensions of the water-way in both pipes and boiler so as to secure a lasting temperature in hot-houses, and other erections ; 1 hope it will not be considered presumptuous in me to offer a few observations on that subject, and leave the impartial reader to decide the question. It is natural that every constructor of hot-water apparatus should be prejudiced in favor of his own peculiar plan, (the child of his own mind) hence it is, that the prescribed dimensions of the conducting pipes differ from half an inch to five or six inches in diameter, according to the different plans of different individuals. I shall merely give my judgment of the proper sizes of pipes, without commenting upon any particular plan. It is my opinion that a hot water apparatus to answer all the desired purposes to which it is applied, should be so constructed as to avoid both the objectionable extremes; therefore, pipes of too large or too small dimensions are equally to be avoided, and this for reasons which I could easily adduce, were it not that Idesire on this occasion to avoid speaking unfavourably of any person’s particular system, but to confine my remarks to boilers formed of a series of pipes, and other plans with water-ways, varying from half an inch to two inches in diameter. These I am willing to admit, have the advantage over boilers, containing larger bodies of water, in as much as they become hot much sooner ; but then it must be recollected that the large body when once heated, will remain hot twice or three times as long as the smaller quantity. I have proved by observation that a four-inch pipe which contains more than three times the quantity of water that a two-inch is capable of receiving in a house of the same temperature, will retain its heat for more than double the length of time that a two inch pipe will. Moreover, when boilers are used that have such small water-way, they require more attention, and cannot be left at night with the same safety, as boilers and pipes containing larger bodies of water, seeing that the former cools so much more rapidly than the latter. Nevertheless, to err in the opposite extreme, by having boilers and pipes to contain very large quantities of water, would be a great waste of fuel, and by no means calculated to answer to the satisfaction of all parties so well as boilers and pipes of medium size. It is my opinion, therefore, that neither in boiler or pipes, should the water-way be less than three inches, or more than four inches, and the boiler should be constructed upon a plan that is without complication, so as to expose the greatest possible extent of surface to the action of the fire, this would be found the most convenient boiler for fuel and effect. By this means also, an opportunity may be afforded of heating several houses from the same fire, at the same time, and with very little more expense for fuel than would be required for a small stove or greenhouse. This I have always considered of the greatest importance, particularly when gentlemen’s establishments are situated at a great distance from coalmines. In all my arrangements where I have heated houses with hot water, I have contrived to have the main body of water in the pipes that run through the house; as it is there that the gardener wants a permanent and lasting heat, this it is that induces me to advocate the use of three and four inch pipes. Moreover, there are other great objections to the use of small pipes varying from half an inch, to two inches particularly, when the boiler is formed of a series of pipes ; in such cases their in-terior becomes, in course of time, furred up from the incrustation formed by the deposition of the various earthy matters held in solution by the water, which naturally causes an accumulation of alkaline earths, &c. an this at length closes up the water-way. Having thus finally expressed my opinion on the demerits of pipes, of small caliber, it must not thence be inferred that I shall err on the other extreme; for, if boilers and pipes capable of containing unnecessarily large quantities of water are used, there will be a great waste of fuel before any heat is communicated to the house, and perhaps a valuable crop of fruit or plants may be destroyed through the gardener not posessing a proper command of heat to prepare against the weather and its frequent sudden and unexpected changes in this uncertain climate. I have found in the course of my experience and observation that in the months of October, November, and December, more especially and, with less frequency, at all periods of the year that up to the hour of!2 o’clock at night, rain may fall in torrents, and the gardener may therefore naturally conclude that during the night no fires will be required either for the greenhouse or conservatory, but how great must be his trouble and surprise to find in the morning eight, or perhaps ten degrees of frost? Now this trouble and inconvenience, I have frequently experienced, therefore, for the benefit of all parties, I beg to repeat here, the opinion I have already given, that boilers of a medium size with water ways not less in any part than three inches, and not more than four inches will be necessary to give the gardener sufficient command of heat, and to afford him an opportunity of protecting the perishable property entrusted to his care, without subjecting himself to unmerited reproach, which is too frequently unjustly heaped upon him for loss of property, through circumstances over which he had no controul; for, to limit a gardener to means when much is expected, can only be compared to setting a man to dig, who has neither legs nor arms ; and creates in the employer an unjust prejudice towards the gardener, through the unavoidable disappointment the former must experience in failing to enjoy the expected benefits of fine crops of fruit, or other horticultural and floricultural productions. Having then explained my objections to pipes of too large or too small dimensions, I shall, in concluding these observations, offer a few suggestions relative to the formation of the furnace and apparatus, generally as a guide to persons who may not have had quite so much practice and. experience as myself. And the firstto which I shall draw the practical gardener's attention, for his own convenience, and for the benefit of his employer, is to see that the mechanist or hot water fixer, furnishes a proper sized furnace door, which should not be less than one foot high by ten or eleven inches wide, for the convenience of clearing out all the clinkers and ashes, and also for lighting and making up the fire the last thing at night, for it is impossible for any man to manage a fire properly with furnace doors such as are used in some hot water apparatus, which do not exceed six or eight inches square; but if a good sized door be used, the gardener is enabled in a country where coals are dear, and wood plentiful, to burn logs of wood, or the refuse from the pruning of trees, &c. where he only wants a little fire through the day, but of course it must be distinctly understood that this description of fuel is not to be depended upon in severe weather, nor for making up of fires for the night. Whatever description of fuel is used, however, I have always found it a great saving to a gentleman, to have a moderately large furnace door; great attention should be paid to its formation, in order to prevent the passage of air through the door-way between the boiler and the fire, the neglect of which precaution, causes a great waste of heat, as air will not support combustion until its temperature is raised to 800 or 900 degrees ; a current of cold air admitted between the fire and boiler through the furnace door, has a tendency to counteract the power of the fire ; to obviate this, I invariably recommend double doors being used to all furnaces, and then if the boiler is so constructed, and set so as to expose (which is the great secret as I have before observed in the formation of all boilers) a large surface to the action of the fire by means of the construction of the flues around it, and thus entirely consume the whole of the gases and carbon before they escape into the chimney, the greater will be the saving of fuel, and the more powerful and effective will be the operation of the apparatus . Indeed, I have no hesitation in saying, that,—if there be a proper quantity of surface of pipe, for the command of the degree of heat required in all extremes of weather, and the furnace be constructed as suggested, and the flues so arranged round the boiler, as to be entirely enveloped with the fire, (which is highly important and ought to be strictly attended to) so that the heat does not escape too quickly into the chimney,—-the fires might bemade up and left without the least risk for eight or nine hours in the coldest nights. In the construction of my Egg-shaped wrought iron boiler, my attention was particularly directed to the construction of a furnace that would obviate the evils complained of in most hot water apparatuses, I mean the great consumption of fuel, in some plans, and the constant attention required, which arise from badly constructed boilers and fire places, but there are several other circumstances connected with hot water which I think very necessary to be attended to, particularly where the boilers are formed of a series of pipes varying from half an inch to two inches in diameter. In the first place, on no account should dirty water be used for filling the boiler and pipes, as it deposits much dirt and accumulation of mud, which, in the course of time, not only injure the boiler but lessens its power, by preventing the heat from immediately acting on the water; also because the accumulated deposit impedes the circulation of the fluid, by diminishing the caliber of the water-way, and ultimately forms a hard incrustation, similar to that seen on the bottom of steam boilers, and frequently ends by causing holes to be burned in the bottom; sometimes, in order to save a little trouble, when hard water is more conveniently obtained than soft or rain water, the boiler is filled with hard water. But the quantity of earthy salts it contains, according to the various component parts of the different strata of earths through which it passes, (as carbonate of lime, sulphate of lime with soda, magnesia, and other saline matter, varying according to the different kinds of soil) renders hard water as injurious as the deposits in dirty water: for, in the evaporation or decomposition of the water when heated to 212 degrees, the earthy particles 1 have just mentioned are deposited, in large quantities, on the bottom of the pipes and boiler; but by the use of rain water, or if convenient filtered o