POWERS or GLASSES. 



325 



said distance is. When that is known, compute how many times those 

 parts of an inch are contained in eight inches, the common standard 

 of sight, and that will give you the numbers of times the diameter is 

 magnified : squaring the diameter will give you the superficies; and if 

 it be an object whose depth or whole contents you would learn, mul- 

 tiplying the superficies by the diameter will show the cube or bulk. 



A- Table of the magnifying Powers of Convex Glasses employed in 

 Single Microscopes, according to the Distance of their Focus; cal- 

 culated by the Scale of an Inch divided into a Hundred Parts : 

 showing how many Times the Diameter, the Superficies, or the 

 Cube of an Object is magnified, when viewed through such Glasses, 

 to an Eye whose natural Sight is at Eight Inches, or Eight Hundreds 

 of a Hundredth Part of an Inch. 



