A watch glass is a small, round piece of glass with a slightly concave surface. It is used in science to hold small amounts of liquids or solids.
The watch glass was used to protect the slide from dust and dirt.
Noun: watch glass (plural: watch glasses).
Adjective: watch-glass.
Verb: to watch-glass.
The word "watch glass" comes from the Old English word "wæcce", meaning "to watch", and "glæs", meaning "glass".
The first recorded use of the word "watch glass" was in the 17th century.
When might a watch glass be used?