Measurement of Length 



17 



Exercise for Student. 



What corresponding correction must be made in the length of 

 the circumference as found by experiment ? 



The above method, or simple modifications of it, 

 may be used in finding the lengths of various parts of 

 objects made up of curved surfaces, and for deter- 

 mining other lengths when the latter do not readily 

 admit of direct measurement. 



Fig. 5. 



Fig. 5 A shows the calipers arranged with the jaws 

 crossed so that the points are directed outwards instead 

 of inwards. Thus arranged, the instrument is of con- 

 siderable service in determining the internal diameter 

 of a vessel. 



EXPERIMENT 5. Arrange the calipers as in Fig. 5 A. 

 Place the points of the jaws just within the mouth of 

 an ordinary tumbler, and adjust the distance between 



H. D. S. 2 



