It is, however, too often the case that, in following out our theories of education, we avoid Scylla only to encounter Charybdis, and so, in specializing our courses of laboratory instruction, there is great danger of falling into the mechanical routine of a technical art, and losing sight of those grand ideas and generalizations which give breadth and dignity to scientific knowledge. That these great truths are as important an element of scientific culture as experimental skill, the author has also endeavored to illustrate, and he has added brief notices of the lives of two noble men of science which may add force to the illustrations. CONTENTS. PAGE I.--SCIENTIFIC CULTURE 5 II.--THE NOBILITY OF KNOWLEDGE 45 III.--THE ELEMENTARY TEACHING OF PHYSICAL SCIENCE 71 IV.--THE RADIOMETER 86 V.--MEMOIR OF THOMAS GRAHAM 127 VI.--MEMOIR OF WILLIAM HALLOWES MILLER 145 VII.--WILLIAM BARTON ROGERS 160 VIII.--JEAN-BAPTISTE-ANDRE DUMAS 181 IX.--THE GREEK QUESTION 203 X.--FURTHER REMARKS ON THE GREEK QUESTION 214 XI.--SCIENTIFIC CULTURE; ITS SPIRIT, ITS AIM, AND ITS METHODS 227 XII.--"NOBLESSE OBLIGE" 267 XIII.--THE SPIRITUAL LIFE 289 ESSAYS. I. SCIENTIFIC CULTURE. _An Address delivered July 7, 1875, at the Opening of the Summer Courses of Instruction in Chemistry, at Harvard University._ You have come together this morning to begin various elementary courses of instruction in chemistry and mineralogy. As I have been informed, most of you are teachers by profession, and your chief object is to become acquainted with the experimental methods of teaching physical science, and to gain the advantages in your study which the large apparatus of this university is capable of affording. In all this I hope you will not be disappointed. You, as teachers, know perfectly well that success must depend, first of all, on your own efforts; but, since the methods of studying Nature are so different from those with which you are familiar in literary studies, I feel that the best service I can render, in this introductory address, is to state, as clearly as I can, the great objects which should be kept in view in the courses on which you are now entering.