An example or two will illustrate my meaning. Children at school are required to commit to memory the tables of weights and measures. The exercise is one of acknowledged and indispensable importance. But it is possible for a child to repeat one of these tables with entire glibness and accuracy, pretty much as he would whistle Yankee Doodle, without any apprehension of the actual things which the terms of the table represent. He may learn to say "sixty seconds make a minute, sixty minutes make a degree, three hundred and sixty degrees make a circle," with no more idea of the things expressed by this formula of words, than the parrot who has been taught to say, "You are a big fool." If the teacher will show the child an actual circle, with the degrees, minutes, and seconds marked, and will let him count them for himself, so that he has a real knowledge of the things, he will then not only commit this formula of words to memory more easily, but the knowledge itself will promote his mental growth. He will be feeding on real knowledge, not on its husks. So in learning about inches, feet, yards, rods, and miles, let the teacher, with foot-rule and yard-stick, show what these measures really are, let him by some familiar instance give the child an idea of what a mile is, and then let the memory be invoked to store up the knowledge gained. So with ounces, pounds, and hundred-weights. So with gills, quarts, and gallons. The common weights and measures are as necessary in the school-room as are spelling-books and arithmetics. The actual weights and measures, so far as possible, should be exhibited, should be seen and handled, and the child's mind made to grasp the very things which the terms express, that is, he should first get real knowledge, and then he should store his memory with it in exact words and forms of expression. This is the true mental order. Knowledge first, then memory. Get knowledge, then keep it. Any other plan is like attempting to become rich by inflating your bags with wind, instead of filling them with gold, or attempting to grow fat by bolting food in a form which you cannot digest.