Themometers For Intense Cold

Experiment lias shown that i troleum ether can be used to measu by its contraction, temperatures se eral hundred degrees below zero c the Fahrenheit scale. At the temper ature at which liquid air boils- 3ln degrees Fahrenheit below zero- petroleum ether still remains in a viscous, or semi-liquid, condition, and continúes to wntract with decrease of temperature.