Page:Popular Science Monthly Volume 37.djvu/28

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Prof. Edward L. Youmans was, of all Americans I have known or heard of, the one most able and most willing to help me. Alike intellectually and morally, he had in the highest degrees the traits conducive to success in diffusing the doctrines he espoused; and from that time to this he has devoted his life mainly to spreading throughout the United States the doctrine of evolution. His love of wide generalizations had been shown years before in lectures on such topics as the correlation of the physical forces; and from those who heard him I have gathered that, aided by his unusual powers of exposition, the enthusiasm which contemplation of the larger truths of science produced in him was in a remarkable degree communicated to his hearers. Such larger truths I have on many occasions observed are those which he quickly seizes—ever passing at once through details to lay hold of essentials; and, having laid hold of them, he clearly sets them forth afresh in his own way with added illustrations. But it is morally even more than intellectually that he has proved himself a true missionary of advanced ideas. Extremely energetic—so energetic that no one has been able to check his overactivity—he has expended all his powers in advancing what he holds to be the truth; and not only his powers but his means. It has proved impossible to prevent him from injuring himself in health by his exertions; and it has proved impossible to make him pay due regard to his personal interests. So that toward the close of life he finds himself wrecked in body and impoverished in estate by thirty years of devotion to high ends. Among professed worshipers of humanity, who teach that human welfare should be the dominant aim, I have not yet heard of one whose sacrifices on behalf of humanity will bear comparison with those of my friend."

Though the volume containing this passage will not be published until after my death, I am very willing that this tribute of admiration to my late friend should be made public now.

I am, faithfully yours, Herbert Spencer.

A committee of the British Association is charged with the collection of information respecting the disappearance or threatened disappearance of rare plants. While instances of complete extinction of any species within recent times may be rare, there are more of local extinction or of apparent extinction for a time, and the cases of threatened extinction are numerous enough to he alarming. A potent factor in the changes that have taken place is "the injudicious action of botanists themselves, and of botanical exchange clubs. The 'dealer' and 'collector' also figure largely in the process, while tourists are not responsible for much damage except indirectly by patronizing dealers. It is too often forgotten that the very rarity of a plant is the sign, and in great degree also the measure, of the acuteness of its struggle for existence, and that, when a plant is in unstable equilibrium with its environment, a small disturbance may have disproportionately great effects."