Invaders from Rigel by Fletcher Pratt

Invaders from Rigel by Fletcher Pratt Astronomers had observed the comet for some time, and had predicted its course. It would collide with Earth. There was no hysteria; scientists were apparently convinced that the results wouldn't be dangerous to life. But Muuray Lee woke up with a feeling of overpowering stiffness in every muscle. He turned over in bed and felt his left elbow, which seemed to be aching particularly - and received the shock of his life. The motion was attended by a creaking clang, and his elbow felt like a complex wheel. Why - he was metal all over! Horror Science Fiction BKNK