The American Garden always takes pleasure . in laying before its readers descriptions of new appliances or inventions of use in horticulture. During the past winter a series of experiments have been conducted by Charles Barnard at his place in Stamford, Conn., in the construction and management of greenhouses. The results of these experiments are here laid before the public for the first time, and they seem to promise an interesting and important change in the entire business of plant culture under glass.

Greenhouses, forcing houses, graperies, propagating houses and other horticultural structures, as now built, are always costly to build and expensive to maintain. Such structures must be built permanently. They cannot be taken down and removed without great loss, and, as a result, are seldom built on leased land. Conservatories attached to houses have to stay with the house, though the family would often be glad to pack it on the furniture van when they move. All such buildings require constant, regular, daily attention. The fires must be looked after night and morning and often in the middle of the night. The ventilators must be opened when the sun shines and closed again at night, or if the sun is obscured by clouds. Hundreds of amateurs have built small greenhouses or conservatories only to abandon them owing to the difficulty of attending to them. The owner is called away on business, and being detained, returns to find the plants burned up by the sun or frozen stiff by the cold. A greenhouse will not run itself and to get a crop of lettuce, Hamburgs or roses; some one must stay near the place day and night for six months without even a half holiday.

The objects sought in the new experiments were exceedingly comprehensive. In the first place, it was sought to make a wall for back and front of a greenhouse that should be absolutely air-tight and, as a result, frost-proof. This has been accomplished by a wholly new method of construction, and it may be interesting to note that when the new house was built at Stamford, and before any plants were placed in it, an oil stove was started on the floor of the house. After burning ten hours the house was not only up to 70 degrees Fahr. inside, but on taking a lamp into the house it would not burn. The oil stove had used up all the oxygen in the air. In a few hours more the stove itself went out for want of air, thus showing that the greenhouse was practically air-tight. In constructing the house attention was paid to convenience in erecting the building and the walls were made in sections, fastened together with screws. The entire building, glass and all, was built under cover, and then by the help of one man it was taken out of doors and set up, in order for immediate use, within two hours. Such a greenhouse can be readily taken down in the spring, stored in a barn and set up again in the fall, or it may be packed on a wagon and carted off with the rest of the furniture.

It is thus possible to place a greenhouse on hired land. Such a house is also very much cheaper than an ordinary house.

The next object sought was to get rid of coal and to save all the trouble of an uncertain, irregular source of heat. A coal fire is never for ten minutes the same. It is at first growing hotter and hotter and then steadily grows cooler till it goes out. A high wind makes a coal fire burn fast. A heavy fog and cloudy sky makes it burn slow. An oil lamp burns with an absolutely unchanging flame as long as the wick is fed with oil. It is the same with gas. Oil and gas are therefore the best fuels for a greenhouse, where the plants should be kept in one uniform temperature from hour to hour and from week to week. Many attempts have been made to burn oil in small conservatories, and almost always with complete failure. The heat is too local. It does not readily distribute itself through the building and the products of combustion are fatal to plant life. In all greenhouses using coal the boiler is always in a separate building, at a serious loss of heat. All the heat of direct radiation from the fire is lost and only the heat from the pipes is available in the house.

In Mr. Barnard's plant-house, oil or gas is burned directly in the greenhouse under a hot-water boiler and the boiler itself gives out a great deal of the heat used to warm the building, while hot-water pipes distribute the heat to other parts. At the same time, all the products of combustion are completely taken out of the building and the plants flourish in as pure an atmosphere as can be found in any greenhouse. The loss of space is very small, as the boiler is placed under the table and only about six square inches of table space is lost. The economy of heat is, therefore, very great, and as the greenhouse is practically air-tight, a single seven-foot gas burner will keep the building warm in any winter weather. It is the same with oil. A single wick of an Adams & Westlake oil stove will keep the house warm in moderate weather, and two wicks in any weather. Such results, it is believed, have never been obtained before. The house is a lean-to eighteen feet long, covered with six-foot hot-bed sash, and stands in an open field on a bleak hill-top; and yet it has been operated by oil or gas through the greater part of the past season.

Naturally enough, in such a tight and warm house the question of ventilation became of the utmost importance. The sash were all screwed down tight, and then in the upper part of one sash, near the centre, a wholly new kind of ventilator was put in. The object was to remove all the hot air from the house and to keep out all back drafts or cold air that might blow in at the ventilator. This has been accomplished in a wholly new way, and in a manner that seems destined to completely change our present methods of running greenhouses. The ventilator is fitted with valves, and by means of a thermostat the ventilator is made automatic. When the heat of the sun raises the temperature to 80 degrees (or to any other degree decided upon) the ventilator opens automatically and permits the hot air to escape. Very soon the house cools down and drops below 80 degrees, when the ventilator closes automatically and remains closed until the temperature rises to 80 degrees, when it re-opens. A cloud passes over the sun and the ventilator closes. If the day is cloudy it remains closed, but if the sun comes out, it opens and remains open till the sun sets or is obscured by clouds. The entire apparatus is under complete control, and may be set for any temperature, according to the crop carried by the house.

The apparatus, at Stamford, worked this last winter for many weeks without attention, and the greenhouse was, as far as ventilation is concerned, perfectly automatic. It practically ran itself and was left for weeks without the slightest attention. It, therefore, dispensed entirely with the labor required to attend to the ventilating.

In like manner, the oil or gas burner can be controlled completely by the sun. A thermostat suspended to the roof close to the glass turns down the flame when the sun warms the house in the morning, and turns it up again at night, or whenever clouds obscure the sun. The new house is thus entirely automatic, self-heating and self ventilating, and the only attention needed is to see that the oil tank is filled about twice a week and that the plants are watered. In the case of gas, no attention is required from the time the gas is lighted in October till it is put out in April.

Mr. Barnard is assisted in his experiments by George A. Weber, a mechanical engineer living at Stamford, and the results of their labors are certainly of the greatest interest to the horticultural world. The details of these important inventions are now being completed, and applications have already been made for patents covering all the improvements.

Naturally enough, in making these researches many new facts in regard to greenhouse construe-tion and management have been discovered. For instance, it has been found that it is not necessary to admit fresh air to such a house; take out the hot and bad air, and fresh air will leak in fast enough through the cracks and through the soil inside the house. Another point: plants in such an atmosphere are remarkably thrifty, and grow with great vigor. The temperature being very uniform, day and night, the plants also grow very fast. The green fly is easily managed, as the air is so still that a few bunches of tobacco stems laid on the hot-water pipes keep the flies in check.

Messrs. Barnard and Weber will probably make arrangements for the manufacture of these auto-matic houses under their patents, and according to designs that will be the outcome of their experiments. The present house is, of course, small; but there seems to be no reason why the same ideas may not be applied to any house heated by steam or hot water, and employing gas or oil instead of coal. The subject certainly suggests many interesting possibilities in the construction and management of all kinds of horticultural buildings.