History of the Typewriter

— 121 — and there is also a shift-key lock which can be brought into instant use. The margin stops are considered to be the most perfect and complete arrangement of the kind to be found on any typewriter. As will be seen on reference to the large illustration of the carriage, which will be seen in Fig. 98, there is a notched scale-bar carrying four margin stops fixed in front of the carriage. These stops may be set at any points decided upon. Should it be desired to go outside these margins, then the small nickel key, just above the top key on the right, acts as a margin release, and throws the stops out of gear, which, however, will be auto- matically recovered when the next line is written. Fig. 98 In die No. 6 Williams the platen can be removed readily and another substituted. If a number of carbon copies are required, the use of a harder platen is recommended, as it presents a less yielding surface and so gives out better copies. The hard platens are ground slightly smaller than the ordinary ones, and the extra thickness of the several sheets of paper thus compensated for, with the result that even under heavy pressure of manifolding, the alignment remains practically unimpaired. In the earlier models, the type-bar was guided to the printing point by means of openings in a metal comb, which was later changed to a slotted guide plate in which the driving arm worked. It then met the front of the quadrant, and passed between the jaws of a type-guide on its way to the paper. There was thus a tendency for the force, when the machine began to get worn a little, to go forward instead of downward, as it should go. To