144 Sir George Shuckburgh Evelyn’s Endeavours 
(§. 12.) Examination of the Dimensions of the Brass Cube, by 
The microscope and micrometer being both adjusted, as well 
with respect to their focus, * as to the value of the micrometer 
scale, the cross wires in their focus were removed to a distance 
being at 27, and the latter at 32, inches,) and then correctly ad- 
justed to this interval on the divided scale. I must observe, 
indeed, that the value of the micrometer scale was not exactly 
ten revolutions of the screw to y 1 - inch, as Mr. Troughton 
designed ; but this measure by the screw,-f* from 6 trials, was 
deficient by — 0,0002 inch ; viz. two ten-thousandths of an 
inch were to be added to each tenth of an inch measured by 
the micrometer, and so in proportion for a less quantity ; but 
this correction is hardly worth notice. 
On the scale. > 
The interval of the cross wires in 
microscope and micrometer 
Interval of ditto, on another part of the 
’ r 126 and 31 = 5,0000 — 
scale, viz. J 
Ditto, ditto - - - - 25 and 30 == 5,0001 + 
Means of the divided Scale. 
from each other of five inches nearly on the beam, (the former 
# The focal length of the object lens is 
The distance of the cross wires from the object lens 
The focal length of the combined eye glass 
Inch. 
°>75 
2,00 
f One Revolution of the screw of the micrometer was 
Each grand division, of which there were ten 
These again subdivided into five, each became 
And half a division, which is very visible, is 
Whence the magnifying power of the microscope becomes 2= 14,2 times. 
r»ru=. Rpvnlntinn of the screw of the micrometer was - == vis inch. 
IOO 
