This section is from the book "The Gardener's Monthly And Horticulturist V24", by Thomas Meehan. See also: Four-Season Harvest: Organic Vegetables from Your Home Garden All Year Long.
It requires much judgment to sow seeds properly. It is an art that cannot be completely taught, though a few hints may be given to put the learner on the track. We must first remember that it requires an effort to push the young growth through the earth, and that all efforts require food. The material in the seed feeds the young plant, and the greater the effort to get through the earth, the weaker it will be when it gets to the top. Many seedlings burn off, because they are too weak to live by the time they get to the surface.
Then we must remember that seeds must have some moisture, and an absence of light. The deduction from all this is that the seeds must be as shallow as possible in the ground, consistently with darkness and moisture. How just to do this must be determined by each sower. It is just here that the point so much insisted on by Peter Henderson is of so much value. By " firming " the earth about a seed, it may be sown much shallower, and yet meet with the necessary conditions of darkness and moisture.