The motive power of these timepieces being produced by the uncoiling of a spring, several parts are introduced which are not found in weight clocks - namely, the spring barrel, fusee, and stopwork. The cover of the barrel ought always to be removed when cleaning the clock, to ascertain the condition of the mainspring, and, if the latter is found at all dirty, it should be carefully removed with a pair of pliers, and cleaned with a little turpentine on a piece of rag. It may be replaced by winding it round its own arbor, which should be screwed in the vice by the squared end. Take hold of the end of the spring with a pair of strong pliers, and wind it as tight as possible; then slip the barrel over it, and carefully let go the spring, holding the barrel tight with the left hand until the spring has hooked. To try that it has hooked securely, before putting it back in the clock, put on the cover, secure the end of the arbor in the vice, and turu round the barrel until you can feel the spring is quite up. A new spring can be put in in the same manner. Always oil the mainspring after it has been handled.

When a new barrel hook is required, select a piece of good steel, and file up a square pivot with a nicely fitting shoulder, and fit in the hole in the barrel; then shape the hook, and rivet in its place.

The fusee is liable to accidents to the clickwork, and when a chain is used, to breakage of the chain hook-pin. There are 2 kinds of line used to connect the fusee with the barrel - catgut and metallic. Metallic lines wear better, look better, and are quite as cheap as gut. To ascertain the length required for a new line, fix one end in the fusee, and wind the line round in the groove till it is filled up; then allow a sufficient length beyond to go round the spring barrel 1 1/2 turn. When catgut lines are used, they should be slightly oiled. The method of fastening the ends is so simple as to need but little description. The fusee end is passed through the hole in the fusee, and tied in a simple knot, the end being slightly singed to render it less liable to slip. The barrel end is passed through the holes in the barrel in the following manner: - Down through the first hole, up through the second, and down through the third; the end is then pushed through the loop formed by passing the line through the first and second holes.

Take special care, in putting together, to see' that the line is free, and on the right side of the pillars. When ready to put the line on in its place, wind it upon the spring barrel by turning the arbor; and when it is all on, and the fusee pulled round as far as it will go, set up the spring one turn, and secure the click in the ratchet. Wind the clock up, carefully guiding the line on the fusee, and see that the stopwork acts properly, and does not cut the line when it rubs against it. The snail in the fusee should catch against the stop directly the fusee grooves are filled up with the line.