1
NB I apprehend the Nonius Double division for both sides to be as
2
regular as the size will permit. and to be depended on within two
3
minutes
4
And I have repeated Convictions, that the meridian is truely settled
6
use to say it had been done by myself
7
Dipping of the needle
8
Before the dipping of the needle be decided, the friction rollers must
10
magnetic line on both surfaces of the needle (again) |
11
10rThe needle must be inserted and both surfaces tried.
12
Thus when the Instrument for the measure of the dipping of the
13
needle was first made for the Royal observatory at Richmond. I
14
found on the 17the of December 1772. to be (as near as I could
15
Judge that day at noon 73 degrees. The following variations are the
16
best credited
17
Years Names of
18
of Obs.observers°.'East
19
_______________________
21
1622Gunter6. 0–42Years at7Minutes P. Year
22
1634Gellibrand4.5–12Years atMinutes p Year
23
1657Bond0.0–23——
27
1745Graham17'. 0
28
1746Graham1730
30
According to the mean of the above Observations, the Variations of
31
the compass, westward has been about 28 degrees 45 minutes in