Molecular disperser

The molecular disperser was a piece of technology employed by the Silurians.

This device was capable of dispersing the Van Allen belt around the planet Earth, allowing for radiation to burn the world's warm-blooded life forms, such as humans, while the reptilian Silurians could live. After the humans, with the aid of the Third Doctor, discovered a cure for the Silurian plague, the new leader decided to employ the disperser as a different way of exterminating the human race.

However, the machine required a great deal of power which they believed they would gain through a human research station that they were draining power from. It was a barrel shaped machine which required two Silurians to carry and had a dish shaped construction on the top which glowed when power entered into it. Once connected to a power source, it was able to convert nuclear energy into microwave rays which dispersed the molecules of the filter that protected the world. The Silurians were capable of controlling the process in order to ensure it did not go out of control and thus destroy the planet. (TV: Doctor Who and the Silurians)

Behind the scenes
In the novelisation Doctor Who and the Cave Monsters, the molecular disperser is called the destructor.