BY THE SAME AUTHOR. ELEMENTARY LESSONS IN HEAT, LIGHT, AND SOUND. With Illustrations. Globe 8vo. 35. SCOTSMAN. -"It is an elementary book, but few elementary books convey anything like so much knowledge of their subjects, and few make the subjects so interesting to a mind coming fresh to them. The large number of illustrations contribute something to this result, but it is due mainly to the expository skill of the author, and to his interesting manner of explaining experiments." EDUCATIONAL REVIEW.-"Well arranged, clearly written. It possesses that rarest of all virtues in a school text-book, scientific accuracy.' SCOTTISH LEADER.-"Prof. Jones is master of an admirably clear expository style; he spares no pains to make each phase of his subject intelligible, and his explanations are aided by numerous diagrams and other llustrations." Separately. HEAT, Is. 3d.; SOUND, Is. 3d. LESSONS IN HEAT AND LIGHT. SPEAKER." An admirable manual. . . . Details of manipulation are clearly explained, and the simplest forms of an appeal to experiment are placed in an attractive manner at the student's disposal." GLASGOW HERALD.-"The same excellent features observable in the previous work, and which gained for it most favourable notices, are to be found in the present treatise. .. Mr. Jones possesses in a high degree the ability to set forth the principles of the subject in a clear and attractive manner, and to the student no better book could be recommended." ELECTRICIAN.-"It is a pleasure to discover a work in which the evident object, an object which has been steadily kept in view throughout the treatise, is to teach and not to cram for examination. We think every elementary student of physics should possess a copy of this work." LESSONS IN HEAT. Separately. Globe 8vo. 2s. 6d. MACMILLAN AND CO., LTD., LONDON. EXAMPLES IN PHYSICS BY D. E. JONES, B.Sc. ་་ LATELY PROfessor of PHYSICS IN THE UNIVERSITY COLLEGE of Wales MACMILLAN AND CO., LIMITED 1920 COPYRIGHT First Edition printed 1888. Second Edition 1893 Reprinted with additions and alterations 1894; with additions and alterations 1917, 1919, 1920 JAN -3 1939 LHG .571 PREFACE THE value of the mental training obtained by solving algebraical problems and geometrical riders has so long been acknowledged that these form an essential part in all mathematical teaching. Although similar practice is quite as necessary in studying physical science, it is by no means equally easy for the student of physics to obtain it, for only the more recent textbooks contain any numerical examples, and these are generally insufficient in number and not carefully graduated. It is quite common to find students who have a correct knowledge of the general principles of physics, and can apply it intelligently in making a physical measurement, but who are yet unable to solve an easy problem or to calculate the results of their experimental work. There can be no doubt that the best way of acquiring the necessary practice is by means of a regular series of quantitative experiments in the laboratory, carried on side by side with the more general work of the lecture-room; but such concurrent work is not always practicable, especially with large classes and in the earlier stages. Just as the student of dynamics has at first to confine his attention to questions of a more or less ideal nature, so in |