The five-inch roll of paper, perforated by the keyboard machine (a hole for every letter), gives the signal by means of compressed air to the mechanism that puts the matrix (or type mould) in position and casts the type letter by letter, each character following the proper sequence as marked by the perforations of the paper ribbon.  By means of an indicator scale on the keyboard the operator can tell how many spaces there are between the words of the line and the remaining space to be filled out to make the line the proper width.  This information is marked by perforations on the paper ribbon by the pressure of two keys, and when the ribbon is transferred to the casting machine these space perforations so govern the casting that the line of type delivered at the “galley” complete shall be of exactly the proper length, and the spaces between the words be equal to the infinitesimal fraction of an inch.

The casting machine is an ingenious mechanism of many complicated parts.  In a word, the melted metal (a composition of zinc and lead) is forced into a mold of the letter to be cast.  Two hundred and twenty-five of these moulds are collected in a steel frame about three inches square, and cool water is kept circulating about them, so that almost immediately after the molten metal is injected into the lines and dots of the letter cut in the mould it hardens and drops into its slot, a perfect piece of type.

All this is accomplished at a rate of four or five thousand “ems” per hour of the size of type used on this page.  The letter M is the unit of measurement when the amount of any piece of composition is to be estimated, and is written “em.”

If this page were set by hand (taking a compositor of more than average speed as a basis for figuring), at least one hour of steady work would be required, but this page set by the Lanston machine (the operator being of the same grade as the hand compositor) would require hardly more than fifteen minutes from the time the manuscript was put into the operator’s hands to the delivery complete of the newly cast type in galleys ready to be made up into pages, if the process were carried on continuously.

This marvellous machine is capable of setting almost any size of type, from the minute “agate” to and including “pica,” a letter more than one-eighth of an inch high, and a line of almost any desired width, the change from one size to any other requiring but a few minutes.  The Lanston machine sets up tables of figures, poetry, and all those difficult pieces of composition that so try the patience of the hand compositor.

It is called the monotype because it casts and sets up the type piece by piece.