The Mkrofcope explained. h\\ 
i inch Is magnified to the length of fix inches, g-icths, 
and 51-iOOth parts of another tenth in length,-we 
therefore without exaggeration fay, every objedt examined 
with this magnifier, is magnified fixty-nine times and 
half, and fo of all the reft. 
The ufe of the preceeding Tables* 
I F the apparent length or breadth of any object be 
required, meafure it by turning the micrometer-fcrew. 
Until the point of the needle has pafted over that part of 
the image under confideration, and you obtain the revo¬ 
lutions agreeable thereto. 
Example I. 
Suppofe you have 20 revolutions, which irt the firft 
table anfwers to 2933, this is equal to 2 inches q-ioths 
^ybdredths; then to find the fize of the objedt itfelf, enter 
the fecond table with the number of the magnifier in ufe 5 
fuppofe the third magnifier* againft which in the column 
entitled Diameter, you will find 6951, which 
fhews the third number magnifies 69 one half times 5 
this fhews the diameter of the object to be no more than 
I-6qth part of two inches and 9-ioths,-whence di¬ 
viding the number in the firft table by the magnifying 
power found againft the number of the magnifier in the 
fecond, the true length of the object itfelf is found to be 
42-1 ooth parts of i-ioth of an inch. 
If any number of revolutions of the micrometer-fcrew 
fhould happen between 10 and 20, 20 and 30, &c. 
the meafure muft be taken out from the firft table twice., 
as follows : 
