Helmholtz H. Popular lectures on scientific subjects
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New York: D. Appleton and Co. 1885. 428 p.In compliance with many requests, I beg to offer to the public a series of popular Lectures which I have delivered on various occasions. They are designed for readers who, without being professionally occupied with the study of Natural Science, are yet interested in the scientific results of such studies. The difficulty, felt so strongly in printed scientific lectures, namely, that the reader cannof see the experiments, has in the present case been materially lessened by the numerous illustrations which the publishers have liberally furnished.The first and second Lectures have already appeared in print; the first in a university programme which, however, was not published. The second appeared in the 'Kieler Monatsschrift ' for May, 1853, but owing to the restricted circulation of that journal, became but little known ; both have, accordingly, been reprinted. The third and fourth Lectures have not previously appeared.These Lectures, called forth as they have been by incidental occasions, have not, of course, been composed in accordance with a rigidly uniform plan. Each of them has been kept perfectly independent of the others. Hence some amount of repetition has been unavoidable, and the first four may perhaps seem somewhat confusedly thrown together. If I may claim that they have any leading thought, it would be that I have endeavoured to illustrate the essence and the import of Natural laws, and their relation to the mental activity of man. This seems to me the chief interest and the chief need in Lectures before a public whose education has been mainly literary.I have but little to remark with reference to individual Lectures. The set of Lectures, which treats of the Theory of Vision, have been already published in the c Preussische Jahrbiicher, ' and have acquired, therefore, more of the character of Review articles. As it was possible in this second reprint to render many points clearer by illustrations, I have introduced a number of woodcuts, and inserted in the text the necessary explanations. A few other small alterations have originated in my having availed myself of the results of new series of experiments.The fifth Lecture, on the Interaction of Natural Forces, originally published sixteen years ago, could not be left entirely unaltered in this reprint. Yet the alterations have been as slight as possible, and have merely been such as have become necessary by new experimental facts, which partly confirm the statements originally made, and partly modify them.The seventh Lecture, on the Conservation of Force, developes still further a portion of the fifth. Its main object is to elucidate the cardinal physical ideas of work, and of its unalterability. The applications and consequences of the law of the Conservation of Force are comparatively more easy to grasp. They have in recent times been treated by several persons in a vivid and interesting manner, so that it seemed unnecessary to publish the corresponding part of the cycle of lectures which I delivered on this subject ; the more so as some of the more important subjects to be discussed will, perhaps in the immediate future, be capable of more definite treatment tnan is at present possible.On the other hand, I have invariably found that the fundamental ideas of this subject always appear difficult of comprehension not only to those who have not passed through the school of mathematical mechanics ; but even to those who attack the subject with diligence and intelligence, and who possess a tolerable acquaintance with natural science. It is not to be denied that these ideas are abstractions of a quite peculiar kind. Even such a mind as that of Kant found difficulty in comprehending them ; as is shown by his controversy with Leibnitz. Hence I thought it worth while to furnish in a popular form an explanation of these ideas, by referring them to many of the better known mechanical and physical examples ; and therefore I have only for the present given the first Lecture of that series which is devoted to this object.The last Lecture was the opening address for the ' Naturforscher-Versammlung, ' in Innsbruck. It was not delivered from a complete manuscript, but from brief notes, and was not written out until a year after. The present form has, therefore, no claim to be considered an accurate reproduction of that address. I have added it to the present collection, for in it I have treated briefly what is more fully discussed in the other articles. Its title to the place which it occupies lies in the fact that it attempts to bring the views enunciated in the preceding Lectures into a more complete and more comprehensive whole.In conclusion, I hope that these Lectures may meet with that forbearance which lectures always require when they are not heard, but are read in print. THE AUTHOR.
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