evertical. This is best done by securing the looking-glass onto one face of a rectangular block of wood. The wood can belaid on the paper and held in position with a weight, thelower edge of the looking-glass should just rest on the paper.Draw a line ABC, fig. 18, on the paper coinciding with… … at B making an angle of about 45° with the normal; at twopoints L, M of this line sticktwo pins vertically into thepaper; look at the mirror ob-liquely, reflexions of the twopins will be seen; move yourhead about until when lookingwith one eye the reflex ions of thetwo pins appear to be in the…
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