This device is helpful in winemaking. The first brewers' saccharometer was constructed by John Richardson in 1784.
It consists of a large weighted glass bulb with a thin stem rising from the top with calibrated markings. The sugar level can be determined by reading the value where the surface of the liquid crosses the scale.
It works by the principle of buoyancy. A Solution with a higher sugar content is denser, causing the bulb to float higher. Less sugar results in a lower density and a lower floating bulb.