INTRODUCTION 9 



1. Calipers (Fr. compas d'epaisseur; Ger. Tasterzirkel) 



2. Slide compass (Fr. compas glissiere; Ger. Gleitzirkel) 



These two types (Fig. 1) differ most widely in the shape of their legs, 

 which in the first are long and curved outwards, to admit of passing 

 around an awkwardly shaped object, and in the second are short and 

 generally straight. Both consist essentially of a metric scale, to one 

 end of which one leg is immovably fixed, while the second leg slides 

 back and forth along the scale, but in the caliper form the legs spread 

 apart from each other upon a pivot placed at a distance from the scale, 

 while in the slide compass the two legs are constantly parallel to each 

 other. 



FIG. 1. Two common instruments. (Made by Hermann, Z-drich.) 

 (The one on the left) Calipers [Fr. compas d'epaisseur; Ger. Tasterzirkel.] 

 (The one on the right) Slide compass [Fr. compas glissiere; Ger. Gleitzirkel.] 



Calipers. There are two forms of calipers with reference to the shape 

 of the measuring scale; (a) the Bertillon form (Fig. 2), with the scale made 

 on a curve, and sliding in an immovable slot upon the movable leg, and 

 (6) the form in which the scale is straight and runs in a separate piece, 

 attached to the movable leg by a pivot (Fig. 1, left hand). Both types 

 are furnished with a binding-screw, which, by fastening the movable 

 leg to the scale may fix a given measurement as long as needed. 



It has been found convenient also to make calipers in two sizes, 

 with varying capacity: 



1. A smaller size, designed mainly for the measurement of heads and 

 skulls, and hence called a Craniometer. Its scale measures 250 mm. 



2. A larger size, designed primarily for taking of thoracic and pelvic 



