When that is done, and he knows pretty well the constellations of this our hemisphere, it may be time to give him some notions of this our planetary world; and to that purpose, it may not be amiss to make him a draft of the Copernican system, and therein explain to him the situation of the planets, their respective distances from the sun, the centre of their revolutions. This will prepare him to understand the motion and theory of the planets, the most easy and natural way. For since astronomers no longer doubt of the motion of the planets about the sun, it is fit he should proceed upon that hypothesis, which is not only the simplest and least perplexed for a learner, but also the likeliest to be true in itself. But in this, as in all other parts of instruction, great care must be taken with children, to begin with that which is plain and simple, and to teach them as little as can be at once, and settle that well in their heads before you proceed to the next, or anything new in that science. Give them first one simple idea, and see that they take it right, and perfectly comprehend it before you go any farther, and then add some other simple idea which lies next in your way to what you aim at; and so proceeding by gentle and insensible steps, children without confusion and amazement will have their understandings opened and their thoughts extended farther than could have been expected. And when anyone has learned anything himself, there is no such way to fix it in his memory, and to encourage him to go on, as to set him to teach it others.
§181. When he has once got such an acquaintance with the globes, as is above mentioned, he may be fit to be tried in a little geometry; wherein I think the first six books of Euclid enough for him to be taught. For I am in some doubt, whether more to a man of business be necessary or useful. At least, if he have a genius and inclination to it, being entered so far by his tutor, he will be able to go on of himself without a teacher.