This interesting thermometer of sorts would make a great addition to a Francophile curiosities cabinet or physic enthusiasts.
This densitometer is still in its original packaging and was made by the French company Dujardin-Salleron (established in 1855). It contains the original glass float with a ballast of mercury at its bottom; this allows it to partially submerge in a liquid and measure the density. (Please note this item the original mercury inside)
Some wear and tear appropriate with the age of this item.
Approx length 30cm