the cube, cylinder , &c. used by the late Sir G. S. Evelyn. 321 
'Diameter of the cylinder. 
The brass pieces were most carefully placed, so that the 
dots were precisely in the direction of the diameters, and the 
surfaces tangents to the circumference. The distance be- 
tween the dots was then compared with 4 inches on the 
scale, from 54 to 58, and the diameter obtained in the manner 
before described. 
Cylinder. ( Diameter. ) 
End 1. 
Readings of the 
Micrometer at the 
Difference. 
Distance 
between the Dots 
in Inches. 
Diameter 
of the Cylinder 
in Inches. 
Mean, 
Scale. 
Dots. 
a to b 
3*3 >7 
c to d 
318 
40 
4 * 
2 73>7 
277 
4,0267022 
4,0270242 
3,9972050 
3,9973660 
J 3 > 997 2 1 
End 2. 
4 » 
4 i 
a to b 
3*3 
do d 
316,2 
272 
275,2 
4,0265363 
4,0268485 
3,9968781 
3,9971903 
J 3.99703 
The mean of these means gives 3,99712 for the diameter 
of the cylinder. 
On a subsequent day I repeated the measurement of the 
diameter, with the following results : 
