Bourdon’s pressure gauge

 Measurement involves little rituals and gestures. When I was a child, my mother would shake our thermometer violently before taking my temperature. In a world that has gone over to digital sensing and labs are dominated by reassuring beeps, such gestures are almost forgotten. But there is one hold-out: tapping the faceplate of a pressure gauge. It is a reminder of a time when measurement was largely mechanical, and its persistence is a tribute to the ingenuity of French instrument maker Charles Eugène Bourdon.