Page:Popular Science Monthly Volume 12.djvu/187

Rh higher and less in the lower notes, the muscles of the larynx really become the determining forces of the ability to sing, and a great deal depends upon securing for them the necessary practice, as for instance for the execution of rapid successions of tones. And herein lies the difference in the voices of singers, the purity of the tone depending upon the accuracy with which they put the vocal cords upon the stretch, while in those whose tones are impure and faulty, the difficulty lies in their inability to give the requisite tension, and of course the muscles take part in the shortcoming. A correct idea of the sound, height, and depth, of the tone which the singer intends to communicate, enables him to strike the correct tension as by intuition, and carries him along its continuance, and through its purity of modulation, until it has ceased.



HEN, in the beginning of the present year, I received a request to deliver before this Institute a lecture on the subject of Evolution, I was at first disposed to excuse myself. Holding religious views which, perhaps, in many respects are not in accordance with those that have commended themselves to you, I was reluctant to present for your consideration a topic which, though it is in truth purely scientific, is yet connected with some of the most important and imposing theological dogmas. Whatever conclusion is eventually reached respecting it will have an influence on them. But there was that liberality of sentiment in your letter—that earnest desire for the ascertainment of truth—that I cast aside these hesitations, and am now here in obedience to your wishes.

Not that I can do justice in an hour to so great a subject, the literature of which ranges through many centuries. It is no new-fangled romance, as some would have us believe. It comes to us from a venerable antiquity. The theorems it expresses, and indeed on which it is based, have long ago been clearly known.

Considering the shortness of the time allotted me, the vast extent of the subject, the special character of this audience, and the nature of your request, I perceive that it is not an elaborate exposition of the evidence in favor of the theory of evolution that I must