Diagonal Scale

Diagonal Scale, an arrangement supplied with most sets of scales for length measurement, for accurate estimation of small fractional lengths. It is not much employed practically. The principle is that if two lines are inclined to each other and meet at any point, their divergence is perfectly uniform as we proceed from that point. If at a distance of ten inches from their intersection the distance apart of corresponding points on the two lines is 1/10th inch, then at a distance of one inch from their intersection the distance apart will be only 1/100th inch, and so on proportionately.