*THE POPULAR SCIENCE MONTHLY.*

occasion to resume the study of a part of the subject, in order to reply to some questions which had been asked me. Greatly to my annoyance, I found that I had apparently lost my grasp of it. The relations involved seemed more complex than they had before appeared to me; and I should there and then have dismissed the subject (not having leisure for mere mental experiments) with the feeling that my strength for mathematical inquiries had diminished. But the subject chanced to be one that I could not dismiss, for, though the questions directed to me might have been left unanswered, the time had come which I had assigned to myself (under certain eventualities then realized) for a complete restatement of my views, enforced and reiterated in every possible way, until a certain course depending upon them should have been adopted, or else the discussion of the matter rendered useless by lapse of time. I soon found, after resuming my study of the subject, that it was far more completely within my grasp than before—in fact, on reacquiring my knowledge of its details, the problems involved appeared to me as mere mathematical child's-play.

The great difficulty in judging of the growth and development of the mind consists in the want of any reliable measure of mental strength—any mental dynamometer, so to speak. Our competitive examinations are attempts in this direction, but very imperfect ones, as experience has long since shown. Neither acquired knowledge, nor the power of acquiring knowledge, is any true measure of mental strength. The power of solving mathematical problems is not necessarily indicative even of mathematical power, far less of general mental power. The ordinary tests of classical knowledge, again, have little real relation to mental strength. It may be urged that our most eminent men have, for the most part, been distinguished, at school or university, by either mathematical or classical knowledge, or both. This is doubtless true; but so it would be the case that they would have distinguished themselves above their fellows at public school or university if the heads of these establishments had in their wisdom set Chinese puzzling as the primary test of merit. The powerful mind will show its superiority (in general) in any task that may be assigned it; and, if the test of distinction is to be the skillful construction of Greek and Latin verse, or readiness in treating mathematical problems, a youth of good powers, unless he be wanting in ambition, will acquire the necessary qualifications even though he has no special taste for classical or mathematical learning, and is even perfectly assured that in after-life he will never pen a sapphic or set down an equation of motion.

In passing, I may note that nearly all our attempted measurements of mind depend too much on tests of memory. It is not recognized sufficiently that the part which memory plays in the workings of a powerful mind is subordinate. A good memory is a very useful servant; nothing more. In the really difficult mental processes, memory—-