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Directions for using the Micrometer, 



Fig. 1. A, The body of the microscope in which a 

 tube is made to slide containing the eye glasses ; this 

 motion is necessary for obtaining distinct vision, b, 

 the slider by which the object is adjusted to distinct 

 vision hi the first case ; c, the plate on which the divi- 

 ded glass is placed, d, the pinion, by which the divid- 

 ed glass is moved. 



Fig. 2. E, The plate on which the objects are to be 

 placed ; this plate is made to turn on a centre, so that 

 the diameter of the object to be measured may be 

 placed at right angles to the motion of the divided 

 glass f, f, two milled headed screws ; to hold the object, 

 g, g, two springs for the same purpose. 



h, The scale, k, the vernier, each division on the 

 scale is equal to the 1000 part of an inch, seen in the 

 place of the object, which is subdivided into ten by the 

 vernier, k, therefore each subdivision is equal to the 

 Tol^o part of an inch seen in the place of the object. 



Great care should be taken to adjust the object to dis- 

 tinct vision ; as on that in a great degree depends the ac- 

 curacy of the measurement. There is a circle on the 

 body A, fig. 1, which is nearly the proper place for the 

 shder, b. The filament of wool sent in its place, with 

 this micrometer, will be found to measure Toh^s of an 



inch. 



T t 



