The instruments - current-meters, sounding apparatus, water-collecting bottles, thermometers, hydrometers, etc. - were all elaborated and improved. [Please select]
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Hydrometers are graduated differently for liquids of different weights. [Please select]
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This instrument is graduated by a standardized scale, and while all hydrometers should read alike in a liquid of known specific gravity, this is generally not the case, so that it is advisable to check a new hydrometer for accurate work against one of known accuracy. [Please select]
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