The mechanism of this lightweight portable is simple. A wheel, carrying raised letters on its edge, is turned until the required character is at the bottom and then pushed down on to the paper. Just before it makes contact, a roller swings up to ink the type, and as the wheel is raised the carriage moves forward to make room for the next letter. The 'Columbia', invented by Charles Spiro, a New York watchmaker, even introduced proportional spacing, moving the paper one, two or three units according to the width of the preceding character.
© Science Museum / Science & Society Picture Library