anaclastic

Anaclastic glasses, sonorous glasses or phials, which are flexible, and emit a vehement noise by means of the human breath; called also vexing glasses, from the fright which their resilience occasions. They are low phials with flat bellies, like inverted tunnels, and with very thin convex bottoms. By drawing out a little air, the bottom springs into a concave form with a smart crack; and by breathing or blowing into them, the bottom, with a like noise, springs into its former convex form.