I had read Tyndall’s lectures on light before I entered Columbia College, but upon reading them again I found there very many things which I had missed before. They did not, of course, describe satisfactorily the physical properties of the luminiferous ether--no lectures ever did--but they did describe, I thought, a bit of the history of physical sciences in the United States which was a revelation to me, and was, as I know now, a most important contribution to the history of the development of scientific thought in the United States. It deserves a prominent place in this narrative, because I had been a witness of this development during the past forty years. * * * * * [Illustration: JOSEPH HENRY (1799-1878)] Joseph Henry, the most distinguished American physicist, together with other distinguished American scientists, among them President Barnard of Columbia College, invited Tyndall, in 1872, to deliver a course of lectures in some of the principal cities in the United States. The object of these lectures was, quoting Tyndall’s words, “to show the uses of experiment in the cultivation of natural knowledge,” hoping that this “would materially promote scientific education in this country.” Tyndall delivered his famous course of six lectures on light in Boston, New York, Philadelphia, Baltimore, and Washington. Joseph Henry, as secretary of the Smithsonian Institution and president of the National Academy of Sciences, took them under his personal direction. The success of these lectures surpassed even the most sanguine expectations. At the farewell dinner to Tyndall some of the wisest scientific intellects of the land were heard, and their words indicated clearly what was the uppermost thought in the minds of the scientific men of the United States when they invited Tyndall. I quote here some of the words spoken by these men. President Barnard of Columbia, the first American expounder of the undulatory theory of light, said: I say, then, that our long-established and time-honored system of liberal education ... does not tend to form original investigators of nature’s truths.... Among the great promoters of scientific progress ... how large is the number who may, in strict propriety, be said to have educated themselves? Take, for illustration, such familiar names as those of William Herschel, and Franklin, and Rumford, and Rittenhouse, and Davy, and Faraday, and Henry. Is it not evident that nature herself, to those who will follow her teachings, is a better guide to the study of her own phenomena than all the training of our schools? And is not this because nature invariably begins with the training of the observing faculties?