While waiting for fermentation to take place in the manure-pile, prepare the frame for your hotbed.
Let it be about a foot and a half in depth at the back, and eight or ten inches deep in front, with sides that slope from the wider boards to the narrower ones. Cover it with glass set in sash. If possible have the sash hinged to the back-board, so that it can be lifted for ventilation without removing it.
The best location for a hotbed is one facing the south, that all possible advantage can be taken of sunshine, and against a building or fence that will protect it on the north from cold winds. Some persons prefer to make an excavation a foot or more in depth for the reception of the heating material, but this is not a matter of much importance. As a general thing it will not be possible to do this in a satisfactory manner while there is frost in the ground, as there will be at the North until after the first of March.
When the first stages of fermentation are over, set the hotbed frame in place, and fill in with five or six inches of very fine, rich soil. This is what your seed is to be planted in.
The young gardener will be surprised at the amount of heat contained in an inclosure like the one described. It will be very similar to the weather conditions of early or middle May out of doors. In it plants will grow healthily and vigorously, provided they are given plenty of fresh air. This is a matter of the greatest importance. Unless your seedlings are aired daily, if the weather is pleasant, they will make a rapid but weak growth, and when the time comes to put them in the cold-frame or the open ground--provided they are alive then--they will be so lacking in vitality that the change will be pretty sure to put an end to them. On every sunny or warm day the sash should be lifted an inch or two, about ten o'clock, and left in that condition until about two. Care must be taken, however, to see that the wind does not blow from a quarter that will drive the cold air in upon the plants. The admission of a cold blast will often be fatal to the tender plants.
Great caution must be exercised in regard to ventilation. The aim should be, at all times, to admit pure, fresh air without allowing cold to enter with it. This may seem a somewhat paradoxical statement, for at first thought it will seem impossible for air from without to come in without taking along with it the cold air which is in circulation outside, but when one takes into consideration the fact that the warm air inside the hotbed meets the air from out of doors at the point of entrance it will be understood that it repels or counteracts it to an extent that makes it safe to open the sash slightly when the outside temperature is nearly down to freezing-point. The hotbed-owner must study existing conditions and be governed accordingly. It is impossible to lay down any hard-and-fast rules to apply in this case.