GROWTH AND DECAY OF MIND. 341 



he had marked out for himself; but the very steadiness and strength 

 of purpose with which he pursues it indicate the degree to which his 

 mind had lost its wonted elasticity. In 1784 and 1785 he was trav- 

 ersing a portion of the same road. But then he was in the prime of 

 his powers, and accordingly we recognize a versatility which enabled 

 him to test and reject the methods of research which presented them- 

 selves to his mind. It was in those years that he invented his famous 

 method of star-gauging, which our text-books of astronomy prepos- 

 terously adopt as if it were an established and recognized method of 

 scientific research. But Herschel himself, after trying it, and satisfy- 

 ing himself that it was unsound in principle, abandoned it altogether. 

 In 1817 he adopted a method of research equally requiring to be tested, 

 and, in my conviction, equally incapable of standing the test ; but he 

 now worked upon the plan he had devised, without subjecting it to 

 any test. Nay, results which only a few years before he would cer- 

 tainly have rejected — for he did then actually reject results which 

 were open to the same objection — passed muster in 1817 and 1818, and 

 are recorded in his papers of those dates without comment. We may 

 recognize another illustration of the loss of elasticity with advancing 

 years, in the obstinacy, one may even say the perversity, with which 

 Sir Isaac Newton, in the latter years of his life, adhered to opinions 

 on certain points where, as has since been shown, he was unquestion- 

 ably wrong, and where, had he possessed his former mental versatility, 

 he must have perceived as much. Compare this with his conduct in 

 earlier years, when for nineteen years he freely abandoned his theory 

 of gravitation — though he had fully recognized its surpassing impor- 

 tance — simply because certain minute details were not satisfactorily 

 accounted for. Many other instances might be cited, were it worth 

 while, to show how the mind commonly changes when approaching an 

 advanced age, in a manner corresponding to that bodily change — that 

 stiffness and want of elasticity, without any marked loss of power — 

 which comes on with advancing years. That old age does not neces- 

 sarily involve any loss of power for routine work, has been clearly 

 shown in the lives of many eminent men of our own era. The present 

 Astronomer Royal for England affords a remarkable illustration of 

 the fact, as also of the associated fact that new work is not easily 

 achieved, nor an old mistake readily admitted or corrected at an ad- 

 vanced age. 



It is well pointed out by Dr. Beard, in the lecture to which I have 

 already referred, that " we must not expect to find at one age the men- 

 tal qualifications due to another age — we must not look for experience 

 and caution in youth, or for suppleness and versatility in age. We 

 ought also to apportion to the various ages of a man the kind of work 

 most suitable to them. Positions which require mainly enthusiasm 

 and original work should be filled by the young and middle-aged ; po- 

 sitions that require mainly experience and routine work, should be 



