Mercury in glass lactometer, paper scale in stem, directions for use on outside of cylindrical case, probably English

Milk inspection became a government responsibility in the late 1800s. This mercury filled glass lactometer would have been placed into a cup of milk. If the milk was pure, the lactometer would float level with the ‘“M” marked on the scale. Other points on the scale indicated the degree to which the milk had been diluted with water. For example, if the lactometer floated at “3” on the scale, the milk contained 25 per cent water; at ‘“2” it was 50 per cent.

Inspection was important to ensure customers were getting what they paid for. The Sale of Food and Drugs Act, 1875, stated that it was illegal to sell products that did not meet customer expectations.