This corresponds, in the Cape instrument, with an excess of the diameters of the holes over those of the cylinders of about i,*mth of an inch - a quantity so small as to imply good workmanship, though it involves a systematic error which is very much larger than the probable error of a single determination of the coincidence point.
The chairs on the British system weigh about 45 or 50 lb each on important lines, though they may be less where the traffic is light, and are fixed to the sleepers each by two, three or four fastenings, either screw spikes, or round drift bolts entered in holes previously bored, or fang bolts or wooden trenails.
9) is only prevented by good fitting of the holes 1 3' y'; and, since the weight of the slide is on one side of the screw, misfit here will have the effect of changing the reading for coincidence of the movable with the fixed web in reverse positions of the micrometer.
9) by holes 7), 0 in the ends of the box, which fit the cylinder closely and smoothly.
The test bar C C, which slides through holes bored in the yoke, is divided near the middle into two parts, the ends which come into contact being faced true and square.