well as if the ideas had taken form in "words. In order to be successful, this would require a very intimate acquaintance with the friend's habits of thought. In fact, we all try to interpret the thoughts of others during silence, but we are generally wide of the mark, because we do not know the peculiar law of association of ideas applicable to each person. There is a general process by which one idea suggests another in all minds, but there are also particular variations. Nevertheless, unless the person is on his guard, fully seventy-five per cent, of his ideas will be known to any one who is accustomed to following the thoughts of others. The first thoughts, which arise in the mind automatically, are limited in number, because the connection with more remote ideas has not yet been made. It is probable that with increased knowledge of the peculiar laws of mental action, great skill will be shown in thus following the ideas of others, and it is clear that such a science of mind-reading would be built upon metaphysical data, just as mathematical data are now necessary factors in estimating the distance and motion of a planet. In some respects the limit of mental penetration may not be as absolute as we imagine. It is certainly not advisable to set limits like those astronomers who claimed that they had discovered the center around which the visible universe is revolving in a mighty orbit. It was found that this so-called center was describing a vast arc of a circle around another center inconceivably distant. The discoveries of the past indicate that others as important are to be made. The horizon recedes, revealing new objects.
In the light of past discoveries it seems highly improbable that so important a physiological gift as a sixth sense could come to us suddenly and mysteriously. This is not the manner in which Nature works. Everything is paid for, and our advantages come only from work and its accompanying natural growth, or by the hereditary transmission of a fortunate balance of powers in a line of ancestors. The first impulse arises from the necessity of work, and from the actions of events which stimulate the ingenuity. The increased activity is accompanied by an increase of fiber or power of continuance. Tyndall has admirably illustrated the fact that this law of mental supply and demand applies with precision to the processes of nature: "No particle of vapor was formed and lifted without being paid for in solar heat. There is nothing gratuitous in physical nature, no gain without equivalent expenditure." It is our tendency to look for theatrical or imposing manifestations of human power not paid for by work, and when a result appears mysterious owing to our ignorance of its source, we too often settle the difficulty in accordance with a convenient and visionary theory. In this way we hear a coincidence called a prophetic dream, no one has adequately estimated the enormous number of dreams that drift through the mind during a lifetime, and when a dream coincides in a measure with an event which takes place long afterward, the assumption then is that some dreams are of a pro-
