evidence of their higher marvels has invariably broken down when submitted to the searching tests imposed by the trained experts whom I maintain to be alone qualified to pronounce judgment upon the matter.
Nothing is more common than to hear it asserted that these are subjects which any person of ordinary intelligence can investigate for himself. But the chemist and the physicist would most assuredly demur to any such assumption in regard to a chemical or physical inquiry; the physiologist and geologist would make the same protest against the judgment of unskilled persons in questions of physiology and geology; and a study of mesmerism, odylism, and spiritualism, extending over more than forty years, may be thought to justify me in contending that a knowledge of the physiology and pathology of the human mind, of its extraordinary tendency to self-deception in regard to matters in which its feelings are interested, of its liability to place undue confidence in persons having an interest in deceiving, and of the modes in which fallacies are best to be detected and frauds exposed, is an indispensable qualification both for the discrimination of the genuine from the false, and for the reduction of the genuine to its true shape and proportions.
And I further hold, not only that it is quite legitimate for the inquirer to enter upon this study with that "prepossession" in favor of the ascertained and universally admitted laws of Nature which believers in spiritualism make it a reproach against men of science that they entertain, but also that experience proves that a prepossession in favor of some "occult" agency is almost sure to lead the investigator to the too ready acceptance of evidence of its operation. I would be the last to affirm that there is not "much more in heaven and earth than is known to our philosophy;" and would be among the first to welcome any addition to our real knowledge of the great agencies of Nature. But my contention is, that no new principle of action has any claim to scientific acceptance, save upon evidence as complete and satisfactory as that which would be required in any other scientific investigation.
The recent history of Mr. Crookes's most admirable invention, the radiometer, is pregnant with lessons on this point. When this was first exhibited to the admiring gaze of the large body of scientific men assembled at the soirée of the Royal Society, there was probably no one who was not ready to believe with its inventor that the driving round of its vanes was effected by light; and the eminent physicists in whose judgment the greatest confidence was placed, seemed to have no doubt that this mechanical agency was something outside optics properly so called, and was, in fact, if not a new force in Nature, a new modus operandi of a force previously known under another form. There was here, then, a perfect readiness to admit a novelty which seemed so unmistakably demonstrated, though transcending all previ-