Es) 920. Aegis 
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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 in 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. BY 
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 
xo3es 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 
slider, b, The filament of wool sent in its place, with 
this micrometer, will be found to measure zoos of an 
inch, 
h pt 
mh ND | 
