Signedprinted on paper scale inside bulb: Electric Storage Battery Co.
on case: J. S. F. Huddleston, Washington St. Boston.
Inscribedprinted on paper scale inside bulb: Philadelphia, Pa, Cat. No. 7165.
FunctionThis is a hydrometer made for testing the specific gravity of solutions of water and sulphuric acid, which indirectly tests the percentage content of sulphuric acid in them. As with most hydrometers, one would let it float in the liquid to be tested and the reading would be the point reached by the liquid's surface on the scale. The reading is affected by temperature so there is a thermometer included inside the hydrometer and the user is expected to make corrections based on the temperature.
In this case, it was most likely used to verify the acidity of batteries.
ProvenanceFrom the Department of Physics, Bowdoin College.