It Measures the Density of Gasses
Puzzle 8 of Yoga Hard Pack
Question is: It Measures the Density of Gasses
and the answer is: DASYMETER
Word Meaning:
DASYMETER — (dated) An instrument for testing the density of gases, consisting of a thin glass globe, which is weighed in the gas or gases, and then in an atmosphere of known density.
Definitions from Wiktionary.