Besides the dolphin fret shown on the Tompion clock in Figure 95 there were other patterns, perhaps the earliest being what is called the "heraldic fret", which was a coat-of-arms with scroll-work on either side. This was not used after 1650, so any clocks bearing this pattern belong to the first half of the seventeenth century. It was early seen that to be accurate a clock must have some contrivance to keep it going while it is being wound. In the old-fashioned house clocks which were wound by merely pulling a string, and in which one such winding served both for the going and striking parts, this was done by using what was called the endless chain of Huyghens, which consists of a chain or string with ends joined together, passing over two pulleys which are placed on the arbors of the great wheels, and which have both spikes and deep grooves in them to prevent the chain from slipping off. To the best clocks in England it was usual to apply the gridiron pendulum of Harrison or the mercurial pendulum of Graham. The length of the pendulum of most clocks made before 1800 was 39 inches; that is, after the long pendulum came into use at all. The earliest were called "bob pendulums", which swung so far at the sides that it was often necessary to cut slits in the sides of the case, if it was hung inside, for it was as frequently hung outside. Many clocks which started with bob pendulums were changed to those having long ones, which about 1680 came very much into fashion. In Mr. Charles Britten's various books on clocks and clockmaking he has gathered together all the minute particulars which are obtainable on this subject, and which are of chief interest to collectors of clocks. Most people are content with one clock, particularly if it be of the "grandfather" variety. The term "clock" was only applied to the bell upon which the hour was rung till well into the fourteenth century, and as late as the time of James I. clocks were known as horologes. Even at the present day the old term has clung to the church-tower time-piece in some of the least-traveled parts of England, and in the quaint and lovely little town of Wells the Cathedral clock is called the "horologe." There are long-case clocks made by Tompion to be found in this country; for of course all the first clocks were of English make. The earliest long-case clocks were made by William Clement about 1680, and within the same year Tompion was making them too. The peculiarities of these first clocks are quite marked and easily distinguished, for the dials were square, and the top of the case lifted off to permit of winding.