172 SEC. 5. MOLECULAR PHYSICS. 



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 Fah. 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 Drs. Hope Coventry 

 and Thomson. 



663. Quin's Saccharonieter. (Obsolete.) 



Dring and Fage, 



664. Dring and Fage Still, for ascertaining the original 

 specific 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. 



664a. Apparatus by Bakowitsch for te sting Alcohols and 

 Saccharine Matter in Liqueurs ; likewise for ascertaining the 

 fatness of butter, and for testing water. 



R. Nippe, St. Petersburg. 



665. Apparatus for determining the Specific Gravity 



of bodies, inclusive of a thermometer. 



Ch. F. Geissler $ Son, Berlin. 



671. Piknometer. Dr. H. Geissler, Bonn. 



671a. Fiknometer 9 for ascertaining the specific weight of 

 small quantities of liquid, with thermometer attached. 



IV. Haak, Neuhaus, Thiiringcn. 



672. Two Sets of Areometers. Dr. H. Geissler, Bonn. 



672b. Micromanometer. 



Royal Mining Academy, Freiburg. 



672c. Drawing of Apparatus for measuring low pres- 

 sures of Gas. Prof. H. McLeod. 



The pressure is measured by compressing a known volume of the gas into 

 a smaller space, and measuring the pressure under the new conditions. By 

 dividing the pressure thus found by the ratio between the original volume and 

 the reduced volume, the original pressure is obtained. See Proc. Phys. Soc. 

 i. 30. 



673. Manometer for Minute Observations, used by A. de 

 la Rive in all his latest researches concerning the propagation of 

 electricity in rarefied gases. 



De la Rive Collection, the property of Messrs. Soret, 



Perrot, and Sarasin, Geneva. 



This instrument, constructed by the Geneva Association for the Construc- 

 tion of Scientific Instruments, consists of two glass tubes dipped in a common 

 mercury trough, of which one is a simple barometric tube serving as a point 

 of comparison, the other communicating on its top with the quantity of rarefied 



