Formerly the greenhouse was the luxury of the rich mansion. It was kept at a high temperature, and was made use of for growing, under cold skies, the golden fruit and the bewitching flowers of the South. Now, and especially since the progress of technics allows of making cheap glass and of having all the woodwork, sashes and bars of a greenhouse made by machinery, the glasshouse becomes appropriated for growing fruit for the million, as well as for the culture of common vegetables. The aristocratic hothouse, stocked with the rarest fruit trees and flowers, remains; nay, it spreads more and more for growing luxuries which become more and more accessible to the great number. But by its side we have the plebeian greenhouse, which is heated for only a couple of months in winter and the still more economically built “cool greenhouse,” which is a simple glass shelter--a big “cool frame”--and is stuffed with the humble vegetables of the kitchen garden: the potatoes, the carrots, the French beans, the peas and the like. The heat of the sun, passing through the glass, but prevented by the same glass from escaping by radiation, is sufficient to keep it at a very high temperature during spring and early summer. A new system of horticulture--the market-garden under glass--is thus rapidly gaining ground. The greenhouse for commercial purposes is essentially of British, or perhaps Scottish, origin. Already in 1851, Mr. Th. Rivers had published a book, _The Orchard Houses and the Cultivation of Fruit Trees in Pots under Glass_; and we were told by Mr. D. Thomson, in the _Journal of Horticulture_ (31st January, 1889), that nearly fifty years ago grapes in February were sold at 25s. the pound by a grower in the north of England, and that part of them was sent by the buyer to Paris for Napoleon III.’s table, at 50s. the pound. “Now,” Mr. Thomson added, “they are sold at the tenth or twentieth part of the above prices. Cheap coal--cheap grapes; that is the whole secret.” Large vineries and immense establishments for growing flowers under glass are of an old standing in this country, and new ones are continually built on a grand scale. Entire fields are covered with glass at Cheshunt, at Broxburn (fifty acres), at Finchley, at Bexley, at Swanley, at Whetstone, and so on, to say nothing of Scotland. Worthing is also a well-known centre for growing grapes and tomatoes; while the greenhouses given to flowers and ferns at Upper Edmonton, at Chelsea, at Orpington, and so on, have a world-wide reputation. And the tendency is, on the one side, to bring grape culture to the highest degree of perfection, and, on the other side, to cover acres and acres with glass for growing tomatoes, French beans and peas, which undoubtedly will soon be followed by the culture of still plainer vegetables. This movement, as will be seen further on, has been steadily continuing for the last twenty years.