V. IIYDKOAIETEKS. 169 



641b. Original Apparatus, by Gay Lussac, for ascer- 

 taining the elastic force of gases and vapours. 



Polytechnic School, Paris. 



641 c. Apparatus, by M. Dumas, for illustrating tlie density 

 of vapours. Conservatoire des Arts et Metiers, Paris. 



642. Sulphurous Acid Tube, to exhibit the flickering stria3 

 which occur, from slight changes of pressure, near the critical point 

 of temperature. Dr. Andrews, F.R.S. 



643. Model, constructed by Professor J. Thomson, to illustrate 

 the results of the experiments by which Dr. Andrews first es- 

 tablished the continuity of the gaseous and liquid states of matter. 



Dr. Andrews, F.R.S. 



V. HYDROMETERS. 



644a. Regnault's Apparatus for estimating the specific 

 gravity of solid bodies. 



Golaz, 24, Hue des Fosses, St. Jacques, Paris. 



645. Compensation Salinometer. 



H. Hadicke, Demmin, Pomerania. 



The compensation salinometer is an areometer especially constructed for 

 measuring the saliferous contents of sea water, or of the water in steam 

 boilers, the readings of which are independent of the temperature of the 

 respective fluids. The dimensions of the same have been so calculated that 

 the increase of the volume of the instrument effected by the expansion of all 

 its constituent materials (i.e., aluminum, or iron and mercury) will avoid 

 the deeper immersion which in the instruments of the ordinary construction 

 would take place in consequence of an increase of the temperature of the fluids. 



646. Apparatus for measuring the Density of Liquids. 



Prof. Dr. Bohn, Aschajfenburg. 



647. Apparatus for determining Vapour Density, on 



Dr. French's system. F. Sartorius, Gottingcn. 



648. Oleometer. An instrument for ascertaining the density 

 of oils. Dring and Page. 



649. Small Sykes's Hydrometer. Dring and Fage. 



650. Barktrometer. Used by tanners for ascertaining the 

 density of bark liquor. Dring and Fage. 



The indication of the steam in degrees, and true specific gravity at 60 F. ; 

 the sliding rule accompanying the instrument enables indications at higher or 

 lower temperature to be reduced to the equivalent at 60 F. 



t, 





