TEXT BOOK - OF PHYSICS.. там BY J. D. EVERETT, M.A., D.C.L., F.R.S., F.R.S.E., PROFESSOR OF NATURAL PHILOSOPHY IN THE QUEEN'S College, belfast. ILLUSTRATED BY NUMEROUS ENGRAVINGS ON wood. SECOND EDITION. R RY UNIVERSITY CALIFORNIA LONDON: BLACKIE & SON, 49 & 50 OLD BAILEY, E.C.; 1883. PREFACE. THIS book is primarily intended as a text-book for elementary classes of Physics. It aims at presenting, in brief space, those portions of Theoretical Physics which are most essential as a foundation for subsequent advances, while at the same time most fitted for exercising the learner in logical and consecutive thought. It does not give minute directions for manipulation; but, avoiding details as much as possible, presents a connected outline of the main points of theory. In order to place science upon an equal footing with the more established studies of ancient languages and mathematics, as a means of,practically training the bulk of our youth to vigorous thought, it seems necessary that science text-books should be constructed upon such lines as these. It is not practicable to make the bulk of the boys in our public schools expert scientific manipulators; but it is practicable to ground them well in the main lines of scientific theory. The aim must be not so much to teach them many facts, as to teach them rightly to connect a few great facts together. Science must be taught them from a liberal, not from a technical stand-point. The book is not intended to supersede oral instruction, but rather to create a demand for amplification and illustration such as the teacher will supply. PREFACE TO THE SECOND EDITION. IN this edition the section on Dynamics has been re-written and made more elementary; a few of the more difficult articles have also been struck out from some of the other sections. British measures have been more largely employed, and everything relating to "absolute units" has been omitted. The book has thus been made easier for beginners, and better adapted to serve as an introductory text-book to the later editions of our "Deschanel,” where the subjects now omitted are fully discussed. Belfast, 1883. CONTENTS. Dynamics, 1. Force, 2. Instruments for measuring force, 3. Gravi- tation units, 4. Equilibrium; Statics, Kinetics, 5. Action and Re- action, 6. Specification of a force, 7. Equilibrium of two forces, 8. Of three forces at a point; Triangle of forces, 9. Resultant and Gravity; Vertical, Horizontal, 23. Centre of gravity, 24. Of volumes, areas, and lines, 25. Of triangle, 26. Of pyramid or cone, 27. Condition of standing, 28. Body supported at one point, 29. Stable, unstable, and neutral equilibrium, 30, 31. Experimental determination of centre of gravity, 32, 33. Tendency of centre of The mechanical powers," 37. Lever, 38. Arms, 39. Weight of lever, 40. Mechanical advantage, 41. Wheel and axle, 42. Pulley, 43. System of pulleys with one cord, 44. System in which each hangs by a separate cord, 45. Inclined plane, 46. Investigation by principle of work, 47. Power parallel to base, 48. Wedge, 49. |