This section is from the book "Spons' Mechanics' Own Book: A Manual For Handicraftsmen And Amateurs", by Edward Spon. Also available from Amazon: Spons' Mechanics' Own Book.
These implements are used for taking inside and outside dimensions where a rule cannot be employed, and for striking out circular figures. Ordinary forms are shown in the annexed diagrams. Fig. 262 is a pair of ordinary plain compasses; Fig. 263, wing compasses; Fig. 264, spring callipers; Fig. 265, inside and outside callipers; Fig. 266, improved inside and outside callipers. The method of using these instruments is sufficiently obvious from their shape. Ordinary useful sizes vary in price from 1 to 5s.