Rsj

fig. 2.

d! it <t

dicular lines to gg on the line ff. From d measure to e; draw a line through this parallel to ab'; from e measure to efe; from d measure to hh on the line (f cf; join hd, he'. Where we use the terms 1 measure from'—as measure from d to b—we mean, in all instances, that the measurement db is to be taken from the copy and transferred to the paper on the board, from the point thereon corresponding to the point d in the copy. Again, when we say < measure from d to V] we wish the pupil to take the measurement db' from the copy, transferring it to the line on the paper corresponding to the line ff in the copy, from the point on the paper corresponding to the point c in the copy. Hence the pupil will observe the use'of datum-lines—as db—from which to take the measurements from the copy to be transferred to the paper on the board on which the facsimile is to be constructed. As a means of enabling the pupil readily to decide on datum-points from which to. take measurements, we explain another method of copying the last figure. Draw any line b' db', assume-any point on it, and draw then a line at right angles to b'db'. The inter--section of these lines will represent the point b' in the diagram just given.. From V measure to /in the copy, and transfer it from b' to the line which is at right angles to ¡/db1 as to f; from /draw a line parallel to VdV. From V measure to b\ or from / to /; join bf. The part b'ffb' will thus-be put in: the part up to (jdcj may thus be put in without the use of a centre-line. The part to e can be quickest put in by using one; however,, it may be done as follows: Measure *from d to h; from h draw a line to m, at right angles to <fd(f; with de or ab' measure to e, and draw through* this a line e'e parallel to dti. From m measure to and from e to e;* join he', he. In the following diagram the use of the circle is shewn.

Example 3, fig. 3. Draw any two lines on the board corresponding to ae, cjgcj in the copy. From g measure to b, c, and d; from g measure to

c

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