Another point to be remembered is that the future association of a fact depends very much upon your system of filing away facts. If you will think of this when endeavoring to store away a fact for future reference, you will be very apt to find the best mental pigeon-hole for it. File it away with _the thing it most resembles_, or to which it has the most familiar relationship. The child does this, involuntarily--it is nature's own way. For instance, the child sees a zebra, it files away that animal as "a donkey with stripes;" a giraffe as a "long-necked horse;" a camel as a "horse with long, crooked legs, long neck and humps on its back." The child always attaches its new knowledge or fact on to some familiar fact or bit of knowledge--sometimes the result is startling, but the child remembers by means of it nevertheless. The grown up children will do well to build similar connecting links of memory. Attach the new thing to some old familiar thing. It is easy when you once have the knack of it. The table of questions given a little farther back will bring to mind many connecting links. Use them. If you need any proof of the importance of association by relation, and of the laws governing its action, you have but to recall the ordinary "train of thought" or "chain of images" in the mind, of which we become conscious when we are day-dreaming or indulging in reverie, or even in general thought regarding any subject. You will see that every mental image or idea, or recollection is associated with and connected to the preceding thought and the one following it. It is a chain that is endless, until something breaks into the subject from outside. A fact flashes into your mind, apparently from space and without any reference to anything else. In such cases you will find that it occurs either because you had previously set your subconscious mentality at work upon some problem, or bit of recollection, and the flash was the belated and delayed result; or else that the fact came into your mind because of its association with some other fact, which in turn came from a precedent one, and so on. You hear a distant railroad whistle and you think of a train; then of a journey; then of some distant place; then of some one in that place; then of some event in the life of that person; then of a similar event in the life of another person; then of that other person; then of his or her brother; then of that brother's last business venture; then of that business; then of some other business resembling it; then of some people in that other business; then of their dealings with a man you know; then of the fact that another man of a similar name to the last man owes you some money; then of your determination to get that money; then you make a memorandum to place the claim in the hands of a lawyer to see whether it cannot be collected now, although the man was "execution proof" last year--from distant locomotive whistle to the possible collection of the account.