Description

A very finely drawn and divided astronomical drawing certainly used for the demonstration of the variation of solar time according to the position of the earth according to the seasons, circa 1786

The outer circle is divided into two times 12.
The middle circle is divided into 360 degrees but the two scales are in opposite directions and offset by 20 degrees (certainly the inclination of the earth’s axis 21° 27′)
The central part partly shows the earth with the polar circle, the two tropics and the equator; between the tropics there is a division going from December 21, the beginning of winter to June 20, the end of spring.
Given all the other small globes oriented according to the ecliptic, the whole could demonstrate the variation of solar time according to the position of the earth according to the seasons.

This “instrument” should be mounted in mobile part or only used like this ?

A contemporary manuscrit note dated 1786 indicated “Made and coming from my father le Baron de Feriet”, on the back from another hand, another manuscrit note, which indicated an English provenance at one point “Mrs Jones Rus[s]el Str. GreenLand do[ck]”.

During the 1780s’, Baron de Feriet was François-Louis de Feriet, an amateur scientist in correspondance with Franklin about his Glass armonica. Franklin wrote about him in 1784 : “Baron Feriet of Versailles, began to work on the same Idea about the Time I receiv’d your Letter; and as he is a very ingenious Man, and has a Hand to execute as well as a Head to contrive the necessary Machinery, I hoped soon to have given you an Account of his Success: but I begin to doubt it, as I hear nothing from him lately.”
We know that François-Louis de Feriet established himself with his family at Versailles in 1781 until 1790 when the Feriet family left France, in reason of the French Revolution, to Germany, then Holland, the USA, exactly New Orleans. François-Louis de Feriet died in 1792 at the New-Orléans.

Some waterstains and tears but without lack.
An unique mathematical astronomical or astronomical scientific device.
33 cm diameter.