Illuminating Art

[major_clanger]

A couple of weeks ago I took my mother on a visit around the historic buildings of Greenwich. We were particularly impressed with the Painted Hall, built as a dining hall for the sailor pensioners in the Naval Hospital but so grand that it was only ever used either for VIP functions or as an art gallery. But it was a couple of details in the spectacular paintings on the walls and ceiling that caught my attention.

Firstly, lets look at this scene.



The balding chap on the left is observing proceedings thorough a collapsible refractor telescope, whilst the angelically-haloed one to the right is wielding an armillary sphere. But what's that the orange toga wearing individual in the middle left is waving around?



Yes, to an electronics engineer it's obvious: a dipole array antenna of some sort, either a Yagi or a log-periodic. Evidently, maritime ELINT was far more advanced in the 1720s than we have hitherto been led to believe; has the secret of Britain's naval success finally come to light?

EDIT As various people have pointed out, it is in fact a cross-staff, an early precursor of the sextant.

Somewhat less frivolously, I was intrigued by the detail of the globe in the mural at the end of the hall.



Let's look more closely:



Britain and Ireland are separate, as was the case at the time, whilst Europe seems familiar enough; France and the Low Countries seem to be depicted together, but that may just be similarity of shading, whilst the Holy Roman Empire, Poland and Sweden can all be distinguished. What is odd though is Africa, which seems to be a sort of layer cake. Intrigued, I looked for contemporary maps, and found Northwestern University's online archive of historical maps of the continent. In particular, this map and this one date from the 1720s or thereabouts, when James Thornhill was painting the hall.

From these maps, it seems that the early 18th Century European concept of northern African geography was indeed to broadly split the region into latitudinal zones. The Mediterranean coast was Barbary (of Pirates infamy); south lay the Sahara, then 'Aethiopia', 'Terra Negritum' and finally 'Guinea' on the south-facing Atlantic coast.

Comments

[(Anonymous)]

http://www.dehilster.info/instrumenten/crossstaff/index.html

[major-clanger.livejournal.com]

Thanks!

[owlfish]

If you want to know more about the log-periodic, look up "cross-staff".

[major-clanger.livejournal.com]

Thanks!

[watervole.livejournal.com]

I'm guessing wildly, but maybe the device was to measure the distance of ships by looking at their apparant height?

[major-clanger.livejournal.com]

Close - as I've noted in my edit, it's a cross-staff, used to measure the height of stars or (rather uncomfortably for the user) the Sun above the horizon.

[hatusu.livejournal.com]

I'm more interested in the influence of Italian Renaissance art, specifically Michelangelo's Sistine Chapel on this painter.