The instruments - current-meters, sounding apparatus, water-collecting bottles, thermometers, hydrometers, etc. - were all elaborated and improved.
The various devices which have been adopted to overcome this difficulty will be described in the account given of the several hydrometers which have been hitherto generally employed.
The plan commonly adopted to obviate the necessity of inconveniently long stems is to construct a number of hydrometers as nearly alike as may be, but to load them differently, so that the scaledivisions at the bottom of the stem of one hydrometer just overlap those at the top of the stem of the preceding.
By this means a set of six hydrometers, each having a stem rather more than 5 in.
Perhaps the main object for which hydrometers have been constructed is the determination of the value of spirituous liquors, chiefly for revenue purposes.
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