_Answer._ They are usually arranged so that the steam will be cut off at some full number of inches of the stroke when the reverse-lever is in each one of the notches. They are therefore located so that the steam will be cut off at 6, 9, 12, 15, 18 and 21 inches, or at 6, 8, 10, 12, 15, 18 and 21 inches of the stroke. A notch is also placed so as to hold the link in mid-gear. In some cases as many notches as there is room for are put into the sectors. The latter seems to be much the best plan, as it gives more gradations in which the valve-gear can be worked, and it is a matter of no consequence whatever in the working of an engine whether the steam is cut off at some full or some fractional number of inches of the stroke. By referring to fig. 144 it will be seen how very great the difference of the distribution of steam must be, as indicated by the 5th, 6th and 7th motion-curves. QUESTION 242. _How long should the reverse-lever be?_ _Answer._ The lever should be sufficiently long so that in throwing the link from full gear forward to full gear backward the handle _A_ will move _not less_ than four times the distance that the link is moved. It is much better to give the end of the handle _A_ five or even six times the motion of the link, as there will then be a much easier action in reversing the engine. This will also make it possible to use longer sectors, and give room for more notches. QUESTION 243. _What provision is made in the reversing gear for overcoming or neutralizing the weight of the link and other parts of the valve-gear?_ _Answer._ Their weight is counterbalanced by the pressure of a spring of some kind. In fig. 103 the two volute springs enclosed in a case, _H_, are used for this purpose. These are compressed by the rod _m_, which is attached to a short arm _l_, on the reverse shaft _A_, when the link is lowered, and consequently the tension of the spring resists the weight of the link when the latter is down or in forward gear. Different kinds of springs are used for this purpose and sometimes are attached to the reverse-lever instead of to the lifting-shaft. QUESTION 244. _What is meant by “setting” a slide-valve?_ _Answer._ It is to fasten the eccentrics in the right position on the axle and to adjust the length of the eccentric-rods and valve-stem so that the valves will give the required distribution of steam. QUESTION 245. _How are the valves of a locomotive set?_