Publisher's Synopsis
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1859 edition. Excerpt: ... surpass certain limits, depending on the nature and length of the thread, which limit is often a semi-circumference, or even a circumference. This is established by arranging, as above, a thread, and placing on the cylinder a weight sufficient to straighten, but not to elongate the thread, and when the equilibrium is well established, turning the cylinder 50, 100, or 180 degrees without changing the axis, and letting it oscillate. The oscillations are counted by means of a mark or index attached to the cylinder; and the time is measured by a good second-hand watch. A corollary from this is that the force of tension is proportioned to the angle of tension. 3d. The times of the oscillations are to each other as the square roots of the weights which stretch the threads. The truth of this law can be exactly established only where the threads have sufficient flexibility to be straightened by a feeble weight, and yet too much tenacity to be lengthened by a considerable one. This law holds good only while the force of torsion of a thread remains the same under the different weights which stretch it. 4. The times of oscillation are as the square roots of the lengths of the threads. The time of oscillation increasing with the length of the thread, the force of torsion evidently must diminish. 5th. The times of oscillation are inversely as the squares of the diameters of the threads. The forces of torsion are as the fourth powers of the diameters of the threads. The knowledge of elasticity of torsion has been applied to determine, by means of the torsion balance, certain fundamental laws of electricity and magnetism, and by means of a small silver thread the density and total weight of the earth. CONSTITUTION OF MATTER. 69. In reference to the...
