The Operations of the Geometric and Military Compass

that of the other, either larger or smaller according to the proportion of the line F G to the A B. Therefore, take with a compass a drafting tool with two hinged legs the line A, which you apply directly upon the scale of the Instrument, placing one leg of the compass in the center of the Instrument and the other upon the point where it falls, which may be, for example, at 60. Then, take also with the compass the line F G, and having placed one of its legs at the point 60, open the Instrument until the other leg falls exactly transversally upon the other corresponding point 60. This configuration of the Instrument will not be changed further, but all the other sides of the proposed Plan will be measured upon the straight scale, and the corresponding distances will be taken immediately transversally for the sides of the new Plan. As, for example, we wish to find the length of the line G H, corresponding to the B C. Take with the compass the distance B C, and apply this from the center of the Instrument directly upon the scale, and having fixed the other leg at the point where it falls, which may be, for example, 66, turn the other leg to the other point 66 transversally corresponding; according to whose measure you will cut the line G H, which will correspond to the B C in that same proportion as the line F G to the A B. And be it noted that when one wishes to transfer a small plan into another much larger one, it will be necessary to make use of the two scales in opposite order, that is, to use the straight scale for the Plan to be made, and the transversal one to measure the lines of the proposed Plan, as for example: We have the Plan A B C D E F, which we want to transfer into another much larger one, that is, upon the line G H, which is to be corresponding to the line A B. To adjust the scales, take