462 
NEW OBSERVATIONS OF THE PLANET MERCURY. 
TABLE XII. 
RATIO OF MICROMETRIC MEASUREMENT OF EQUATORIAL DIAMETER TO POLAR MERCURY 
' WITH THREAD CORRECTIONS ONLY. 
* Polar taken at 7".80 throughout. 
Now this is a point susceptible of some nicety, for it is not, properly speak 
estimate at all, but a matter of direct observat 
be curved one way or the other. 
Tl 
eye is very quick 
determination is in truth a criterion of 
of cusp or of terminator visibl 
So quick is it, indeed 
o 
of th 
We come now to adeduction of some interest which follows ft 
<^»'^ o 
1 
best criterion for the apparent phase, and 
of the centre of the terminator and of the cii 
- at the centre of the i9.vm',,.ni... ^l. :ii 
Since 
m that they 
micrometric 
fainter 
at 
