144 SEC. 5. MOLECULAR PHYSICS. 



658. Clark's Import Hydrometer (obsolete). Formerly 

 used for ascertainiag the strength of spirits imported. 



Dring and Page. 



The same in principle and construction as the one for export, only having 

 nine extra or intermediate weights, called per cent, weights. This class of 

 instrument was only used for determining the strength of spirits imported, 

 and was adjusted slightly in favour of the importer. 



659. Set of Six Twaddell's Hydrometers. Used for 



ascertaining the density of solution ; principally used in trades 

 for which no special instrument of the kind is constructed. 



Dring and Page. 



The divisions on these instruments are so placed as to indicate equal dif- 

 ferences of gravity. The specific gravity of a fluid is formed from the indi- 

 cation of this scale by multiplying by 5, cutting off 3 decimal places, and 

 prefixing unity. ^ 



655. Specific Gravity Instruments, for testing liquids 

 from 650 to 900 spec. grav. L. Oertling. 



659a. Fahrenheit's Metal Hydrometer. 



The Physical Science Laboratory of the Technological 

 Institute at St. Petersburg (Russia). 



The theory of this instrument has been described and illustrated by an 

 example by E. Lenz, Academician, in the " Bulletin physico-inathematique 

 " de 1'Academie des Sciences," Vol. XV., 1857. 



660. Thermo-Dilatometer, by Baudin, showing the strength 

 of alcohol in lOOths. M. Baudin, Paris. 



661. Thermo-Dilatometer, by Baudin, showing the al- 

 coholic strength of wines and other liquids. 



(The last two instruments are the property of the " Conservatoire 

 des Arts et Metiers.") M. Baudin, Paris. 



662. Dring and Fage Sac char ometer, for ascertaining 

 the density of brewers' worts. Dring and Fage. 



Used for determining the density (in pounds weight) of a barrel of wort, 

 of 36 imperial gallons, in excess of the same quantity of distilled water at a 

 temperature of 60 Fht. The rule accompanying the instrument shows the 

 weight of the residuum if a barrel of wort were evaporated to dryness ; also 

 the amount of proof spirit to be obtained, and the specific gravity. 



This instrument was the joint invention of Messrs. Dring and Fage, and 

 perfected by the valuable experiments and calculation of Dr. Hope Coventry 

 and Thomson. 



663. Quin's Saccharometer. (Obsolete.) 



Dring and Fage. 



664. Dring and Fage Still, for ascertaining the original 

 gravity of a wort from a sample of beer. Dring and Fage. 



Used by the Excise and Customs when making the allowance for drawback 

 on export beer. 



