Lastly, the lessons of these spontaneous apparitions have been confirmed and widened by actual experiment. It is plain that just as we are not confined to noting small spontaneous telepathic transferences when they occur, but can also endeavour to reproduce them by experiment, so also we can endeavour to reproduce experimentally these more advanced telepathic phenomena of the invasion of the presence of the percipient by the agent. It is to be hoped, indeed, that such experiment may become one of the most important features of our inquiry. The type of the experiment is somewhat as follows. The intending agent endeavours by an effort at self-concentration, made either in waking hours or just before sleep, to render himself perceptible to a given person at a distance, who, of course, must have no reason to expect a phantasmal visit at that hour. Independent records must be made on each side, of all attempts made, and of all phantoms seen. The evidential point is, of course, the coincidence between the _attempt_ and the _phantom_, whether or not the agent can afterwards remember his own success.[126] Now the _experimental_ element here is obviously very incomplete. It consists in little more than in a concentrated desire to produce an effect which one can never explain, and seldom fully remember. I have seen no evidence to show that any one can claim to be an adept in such matters--has learned a method of thus appearing at will.[127] We are acting in the dark. Yet nevertheless the mere fact that on some few occasions this strong desire has actually been followed by a result of this extremely interesting kind is one of the most encouraging phenomena in our whole research. The successes indeed have borne a higher proportion to the failures than I should have ventured to hope. But nowhere is there more need of persistent and careful experimentation;--nowhere, I may add, have emotions quite alien from Science--mere groundless fears of seeing anything unusual--interfered with more disastrous effect. Such fears, one hopes, will pass away, and the friend's visible image will be recognised as a welcome proof of the link that binds the two spirits together. The case which I quote in Appendix VI. F illustrates both the essential harmlessness--nay, naturalness--of such an experiment, and the causeless fear which it may engender even in rational and serious minds.