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by means of an eye-piece micrometer. As, however, 

 this does not measure the object directly, but only its 

 image, the first part of the process makes it more 

 complicated. However, this portion is usually 

 attended to by the manufacturers. The eye-piece is 

 provided with a slot, into which a micrometer is fitted. 

 A micrometer with the same divisions as the eye- 

 piece micrometer is placed upon the stage and the 

 objective focussed upon it. It is now observed how 

 many of the divisions of the eye-piece micrometer 

 are contained in the magnified division of the stage 

 micrometer, and the resulting figure is placed in the 

 sub-division under the objective. To determine the 

 actual size of an object, this is now placed on the 

 stage and, noting the number of divisions which cover 

 it, these are divided by the number on the card, and 

 the resulting figure gives the actual size. Suppose 

 the figure on the card is 8.0 and the image of the 

 object covers 40 of the spaces which are divided into 

 -jL millimeters, the size of the object would be ^ or 

 L millimeter ; or expressed in inches, (25.4 mm. equal 

 to 1 inch) about -fa. 



