The first clocks were comparatively by large and were stationary. Portable ones appeared about the beginning of the fourteenth century, though the inventor is not known, nor the exact time or place of invention. When portable clocks were invented, the motive power must have been changed from weights to main-springs, and this change in motive force marks an era in the development of the clock. The introduction of the pendulum as a regulating agent was, however, the greatest event in clock development. This invention has been credited to Huygens, a Dutch philosopher, who was certainly, if not the discoverer of the pendulum, the first to bring it into practical use, about 1657. Credit for inventing the pendulum is also claimed for Harris, a London clockmaker; for Hooke, the great English philosopher; for a son of Galileo, the celebrated Italian scientist; and for others. The modern watch is in reality but a developed type of the clock. Watches were made possible by the introduction of the coiled spring as motive power, instead of the weight. The coiled spring came into use near the end of the fifteenth century, though it is not known where or by whom it was invented. Watches were not introduced into general use in England until the reign of Elizabeth, and then on account of the cost they were confined to the wealthy. At first watches were comparatively large and struck the hours like clocks. After the striking mechanism was abandoned, they were reduced in size and for a time were considered ornamental rather than useful. They were richly adorned with pictures in enamel and with costly jewels. They were set in the heads of canes, in bracelets, and in finger-rings. Watches and clocks had originally only one hand, which indicated the hour. Minute and second hands were added later. Devices have been introduced to counteract the effect of temperature on the mechanism of time-pieces, so that they run uniformly in all kinds of weather. Within recent years clocks operated with electricity have been invented. With the advent of clock and watch manufacture by machinery, the cost has been so reduced that practically any one may own an accurate time-piece. The United States is one of the foremost countries of the world in the manufacture and sale of clocks and watches. CHAPTER XVI SOME MACHINES THE SEWING MACHINE