PARALLELISM IN PRINTING.

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In drawing plans, and in making cabinet and joinerywork, this property of parallel lines is frequently madeuse of. An instrument is employed, called a T square,because it is formed of two pieces at right angles, MN,OP, fig. 3, pi. % and has the’ shape of this letter. Thethicker and projecting branch or stock MN, is placedalong the side AO, of a plank ABCD ; the other partOP being perpendicular to MN, it follows that all theright lines, AB, EF, traced along the branch OP, are pa-rallel lines.

Besides the common T square, there is another in use in Britain ,which seems to have several advantages. It has a moveable blade,and an arc of a circle divided into degrees, so that it is useful fordrawing parallel lines, both at right angles with the stock and atany degree of obliquity. Fig. 4, represents such a T square, themoveable blade of which, AB, can be set to any angle, and fixedto the arc G, by the thumb-screw D. The action of the thumb-screw D, and of a clamp E, may be more distinctly seen at fig. 4 double,as likewise the screw F, upon which the blade turns as a centre.

The screw F being withdrawn, permits the blade to be taken out,and the edges repaired, if they should receive any injury from wearor accident. The arc G, being divided into degrees, permits theblade to be placed at any angle where it may be fixed by the thumb-screw D.

When troops are to be ranged in columns, that is tosay, parallel masses, AB, CD, &c. fig. 5, guides or flugelmen, A, C, E, G, are placed in a right line, and at equaldistances; each body of troops is then formed into a lineperpendicular to the right line ACEG; and the officersare then certain that the different masses or columns areparallel to each other.

In writing and in printing, the letters are ranged in linesalways equi-distant and parallel. The letters, individually,consist of parts which are right lines.—the strokes of the m,and n, for example, which are also equi-distant and parallelThe only difference remarked in them is, that these paral-lels are perpendicular to the lines in roman type; theyare inclined to the right in the running hand and in ital-ics, and inclined to the left in some old black letter.

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