The market-gardeners around the great Northern cities, finding that winter products were coming from the South and from warmer regions, began to build hothouses and by means of steam and hot-water pipes to make warm climates in these glass houses. Many acres of land in the colder sections of the country are covered with heated glass houses, and in them during the winter are produced fine crops of tomatoes, lettuce, radishes, cauliflowers, eggplants, and other vegetables. The degree of perfection which these attain in spite of having such artificial culture, and their freshness as compared to the products brought from a great distance, have made winter gardening under glass a very profitable business. But it is a business that calls for the highest skill and the closest attention. [Illustration: FIG. 83. SETTING PLANTS IN A COLD-FRAME] No garden, even for home use, is complete without some glass sashes, and the garden will be all the more successful if there is a small heated greenhouse for starting plants that are afterwards to be set in the garden. =Hotbeds.= If there is no greenhouse, a hotbed is an important help in the garden. The bed is made by digging a pit two feet deep, seven feet wide, and as long as necessary. The material for the hotbed is fresh horse manure mixed with leaves. This is thrown into a heap to heat. As soon as steam is seen coming from the heap the manure is turned over and piled again so that the outer part is thrown inside. When the whole is uniformly heated and has been turned two or three times, it is packed firmly into the pit already dug. A frame six feet wide, twelve inches high on the north side and eight inches on the south side and as long as the bed is to be, is now made of plank. This is set upon the heated manure, thus leaving six inches on each side outside the frame. More manure is then banked all around it, and three or four inches of fine light and rich soil are placed inside the frame. [Illustration: FIG. 84. THE GLADIOLUS] The frame is then covered with hotbed sashes six feet long and three feet wide. These slide up and down on strips of wood let into the sides of the frame. A thermometer is stuck into the soil and closely watched, for there will be too much heat at first for sowing seed. When the heat in the early morning is about 85 deg., seeds may be sowed. The hotbed is used for starting tomato plants, eggplants, cabbage plants, and other vegetables that cannot stand exposure. It should be made about eight or ten weeks before the tender plants can be set out in the locality. In the South and Southwest it should be started earlier than in the North. For growing the best tomato plants, and for such hardy plants as lettuce and cabbage, it will be better to have cold-frames in addition to the hotbed; these need not be more than two or three sashes.