I remember reading about this in Mason & Dixon. Mason, who worked at the Royal Observatory, was the one who identified this mountain as the best place for the experiment (and was asked to help with it but declined).
IIRC, it was partly the Mason Dixon line that inspired this experiment. They noticed syatematic errors in the line because their plumb bobs were deflected by gravitational pull from local terrain. At the time they speculated it was because of the Alleghenies, though it was probably more localized variations in gravity.
> Using the stars as a reference, Maskelyne’s team found that the plumb lines on either side of the mountain pointed just 0.0152 degrees apart.
I'm really interested in knowing how they could get such a precise measurement (even accounting for errors), especially in the field (outdoor). There's no figure depicting the apparatus they used, I wonder how it looked like.
Sometimes, I just ponder at how ignorant I am. If I was tasked with the same assignment, I'd definitely fail and this was performed 250 ago!
> The first caliper with a secondary scale, which contributed extra precision, was invented in 1631 by the French mathematician Pierre Vernier (1580–1637).[1] Its use was described in detail in English in Navigatio Britannica (1750) by mathematician and historian John Barrow.[2] While calipers are the most typical use of vernier scales today, they were originally developed for angle-measuring instruments such as astronomical quadrants.
So it would have been a contemporaneous technique with that initial angle measurement, and the use of a Vernier scale for angular measurements would have itself been common.
I remember reading about this in Mason & Dixon. Mason, who worked at the Royal Observatory, was the one who identified this mountain as the best place for the experiment (and was asked to help with it but declined).
IIRC, it was partly the Mason Dixon line that inspired this experiment. They noticed syatematic errors in the line because their plumb bobs were deflected by gravitational pull from local terrain. At the time they speculated it was because of the Alleghenies, though it was probably more localized variations in gravity.
> Primary sources:
> Maskelyne’s notes: https://doi.org/10.1098/rstl.1775.0050
> Hutton’s notes: https://doi.org/10.1098/rstl.1778.0034
> Cavendish’s notes on his own experiment: https://doi.org/10.1098/rstl.1798.0022
I got to reproduce Cavendish’s experiment when I was a student. Love that we can easily read the primary source today, archived and indexed by DOI.
> Using the stars as a reference, Maskelyne’s team found that the plumb lines on either side of the mountain pointed just 0.0152 degrees apart.
I'm really interested in knowing how they could get such a precise measurement (even accounting for errors), especially in the field (outdoor). There's no figure depicting the apparatus they used, I wonder how it looked like.
Sometimes, I just ponder at how ignorant I am. If I was tasked with the same assignment, I'd definitely fail and this was performed 250 ago!
Maybe something similar to a vernier caliper.
From Wikipedia:
> The first caliper with a secondary scale, which contributed extra precision, was invented in 1631 by the French mathematician Pierre Vernier (1580–1637).[1] Its use was described in detail in English in Navigatio Britannica (1750) by mathematician and historian John Barrow.[2] While calipers are the most typical use of vernier scales today, they were originally developed for angle-measuring instruments such as astronomical quadrants.
https://en.wikipedia.org/wiki/Vernier_scale
So it would have been a contemporaneous technique with that initial angle measurement, and the use of a Vernier scale for angular measurements would have itself been common.