History of the Typewriter

—219— the operation of the machine. The dog is so adjusted, that when a key is struck, it is released from a tooth in the rear escapement wheel and brought into contact with the next tooth in the front escapement wheel. As soon as the key is released, the rocker goes back to its first position, and engages in a tooth in the rear escapement wheel. It is claimed that this arrangement of wheels and single dog gives a greater speed than any previous form of escapement. The Smith-Premier, No. io. This machine must not be mistaken for the L. C. Smith Visible previously dealt with in this chapter. The appear- ance of the machines is very different, but the similarity of names may cause some confusion if not explained. It is a visible writer, and retains many of the features of the non-visible machine. Thus, the keyboard is still arranged in straight lines, thus assisting in the acquire- ment of “ touch ” writing ; there is a key for every character, and the platens can be removed and interchanged as before. In the newer model, ball-bearing typebars are intro- duced and the back-spacer key is added to the keyboard. Like so many other machines, it has the “ speediest escape- ment ever devised,” and the change of colour of ribbon, when the bi-chrome ribbon is used, is effected from the keyboard. This is an advantage, as in the L. C. Smith machine, as one example only of many, it is necessary to reverse a small plunger right in the heart of the machine under the ribbon carrier. Coming to details, the typebars in the machine under notice are hung on a single row of ■} inch steel balls with facilities for adjustment. This is the size of ball usually employed in a bicycle pedal, and each ball is strong enough to bear a weight of several hundred pounds, with the result that these parts of the machine are practically indestructible. Some of the bearings have, it is said, been put to a mechanical test of 10,000,000 strokes under many times the pressure of ordinary writing, without showing looseness or wear. It is interesting to note that ten million letters, side by side, would write a line twelve miles long. The typebars are covered whilst in the basket, and only come into sight when actually nearing the printing point. This is an advantage to the sight of many operators, who cannot stand the typebars continually “ bobbing up