In order to force vegetation successfully, we must have control of heat which can be applied at will to both the roots and the foliage of the plants we are cultivating. This control of heat is acquired in green and hot houses by using fire heat either directly, as when a furnace and its flues warm the building; or indirectly, by steam and hot water conducted about the house in pipes. Flues have many disadvantages : they are very liable to smoke; they always heat the house unequally, overheating the end nearest the furnace, while the other extremity of the house may be cold.

Steam or hot water by its circulation reduces the inequality, the cooling or condensing of the water or steam at the point of the circulation most distant from the boiler making a species of vacuum which is filled by more hot water from the fountain, the cooled portion hastening back to take its place in the boiler, thus keeping up an equable heat in all parts of the house.

To illustrate the advantage which hot-water heat has over manure when applied to hot-beds, I will give the experience of a practical man near Boston, who has, I think, proved that climate and soil are under the control of the will of the cultivator, and that Massachusetts may be a worthy rival to New Jersey in market gardening.

The advantage which fire has over manure has long been known, and made use of, in England; and more than ten years ago I urged the market gardeners, in a book called "Country Life," to imitate the European example. In that treatise I gave not only the theory and facts, but plans of advantageous methods of using hot water. But farmers and gardeners are proverbially slow about making improvements; and only within a few years have the most enterprising begun to change their system.

But to return to my example. Mr. Augustus Calder is the son of a market gardener who lives in West Roxbury, a suburb of Boston, who has cultivated for many years a cold gravelly hillside farm as a market garden. Manure, labor, and hotbeds have induced his unfavorable soil to furnish profitable occupation to father and sou.

Wearied with hauling manure, and the constant attention and labor which manure-heated hot - beds require, Mr. Augustus Calder last year determined to try what he could do with fire heat. Against the advice of his friends he abandoned the old frames, and built a simple span-roofed hotbed, running north and south, out of his hotbed sashes. He raised the front of the house 1 foot from the ground, and dug a cellar under it 4 feet deep, and made it 10 feet wide. The sashes meet on a simple ridge of plank 6 feet above the walk which occupies the center of the house; the ridge is kept in place by the fixed sashes, every other one being used like a rafter to give strength to the roof. Movable sashes are hinged at their lower end and shut into the ridge, where they are confined by a hook, hasp, and staple; the joints of the fixed sashes are covered by half-round moldings which are attached to the edges of the movable sash. The crack along the ridge is made water-tight in the same way. On each side of the walk, which is 2½ feet wide, are tables 3 feet from the floor and 3) feet wide; these tables are supported on cedar posts; 1 foot of the upper part of the table being filled when the house is in use, either with earth or pots.

This building, 150 feet long, is heated by hot-water pipes, which carry the water of a small boiler around the house and under the tables, insuring equal temperature in all parts, and giving both bottom and top heat to the growing plants. In such a building there are very obvious advantages. There is plenty of room for the workman to move about; manage his beds; water, weed, transplant, etc. He can transplant in cloudy and bad weather; can raise or lower the temperature at will; can, by the introduction of partitions and an extra pipe, heat one part more than another; can grow a variety of crops at the same time or in sequence, and need only change the soil in his beds once a year.

This experiment was watched with great interest by Mr. Calder's neighbors, who could not believe success could follow such an abandonment of the traditions of the fathers. But success came in the shape of firm, hard, dark-green heads of lettuce before the hot-bed lettuce had begun to make heads at all. His lettuce crop all sold quickly as soon as it was ready for market; and his cucumbers, radishes, and tomatoes carried his profits on to the end of the season.

A particular advantage follows this method of forcing lettuce; in hot-bed lettuce some of the outer leaves are sure to be touched or burned by the hot ammoni-acal vapor of the manure; every leaf so injured decays and dies down to the stem; all these rotten leaves must be removed before the head is ready for sale. Of course such a depilatory process reduces the value and hurts the attractive appearance of the head. None of Mr. Calder's heads of lettuce suffered any more than if they were in the open ground, and could be removed directly from the table on which they grew to the barrel for market.

Encouraged by this success, he determined to enlarge the field of his operations by more houses and different crops. During the summer he built three houses, 160 feet long, and of the same general dimensions, in the ridge - and - furrow style, all to be heated by hot water from a single boiler. These houses he has devoted to lettuce, cucumbers, strawberries, and violets, for with the true spirit of the inventor and radical, he decided to add flowers to the crops he had always cultivated, and selected violets for his first experiment.

To give the violets every chance for success, he tried to learn how florists cultivated them. He found the plants were struck from cuttings in the summer, and were wintered in pots or cold frames until February, when they were brought into the green-house and placed near the glass, and exposed to a high degree of heat, the temperature being maintained as high as 70° by day and 50° by night. The soil in the pots and frames was the same as that used for all other green-house plants.