Another, subsequent type, was developed by Millis Jefferis of MD1 known as the "Lead Delay switch" or officially "Switch, No. 9, L Delay". Instead of relying on the chemical action of a corrosive liquid on metal (which was subject to temperature variation), it used a piece of metal under stress - the metal in question being a lead alloy that was extremely affected by mechanical creep. A piece of this lead was notched to a set diameter, the diameter setting the time delay. When the starting pin was removed, this wire was placed under tension by the spring-loaded striker, and began to gradually stretch. After certain time it would snap at the notch and allow the striker to hit the percussion cap.