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. 1840 edition. Excerpt: ... force of the main-spring, which increases or diminishes the arc which the balance describes; or it may be done, by strengthening or weakening the hair-spring, which will cause the balance to move quicker or slower. The hair-spring, otherwise called the pendulum-spring, q, Fig. 3, is fixed to a stud, upon the plate, c, by one end, and is attached to the verge of the balance, by the other. The regulation is effected by means of what is called the curb. This is a small lever, z, Fig. 3, projecting from a circular ring, rr, which may be considered as its centre of motion, but perforated with a hole through the centre, large enough to contain the hair-spring within it. A circular groove is turned out in the upper plate, nearly concentric with the balance, and the ring rr fits into this. Both are turned rather largest at the bottom, in the manner of a dove-tail; but the ring, being divided at the side, opposite to the lever, z, can be sprung up, and rendered so much smaller, as to get it into the groove; and, being once in, the elasticity of the DESCRIPTION OF A WATCH. 207 ring expands it, so as to fill the groove completely. In this state, it may be considered as a lever, which describes a circuit round the verge, as a centre; and the end of it points to a divided arc, engraved on the upper plate, one end of which is marked F, and the other, S, denoting that the index, or lever, z, is to be moved towards one or the other, to make the watch move faster or slower, as its regulation requires. The manner of its operation is thus; the end of the lever, or index, z, continues within the circle, a small distance towards its centre, and, passing beneath the outer turn of the spiral spring, 5, has two very small pins rising up from it, which include...
