142 SEC. 5. MOLECULAR PHTSICS. 



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. 



644. Surface Spring Indicator. 



H. Hadicke, Dcmmin, Pomerania. 



The indicator was constructed by the exhibitor, and executed from his 

 drawings by Messrs. Blanche and Co., in Merseburg. The piston has been 

 replaced by a surface spring, and the construction aims 



1. At avoiding the friction of the piston of the indicators hitherto 



in use. 



2. Avoiding the slackness of the piston. 



3. Avoiding the points of the diagram of machines of rapid motions 



produced by the mechanical momentum of the piston. 



645. Compensation Salinometer. 



H. Hadicke, JDemmin, 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. 



Professor Dr. JBohn, Aschajfenburg. 



647. Apparatus for determining the Vapour Density, 



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



648. An Oleometer. An instrument for ascertaining the 

 density of oils. Dring and Fagc. 



649. A Small Sykes's Hydrometer. Dring and Fagc. 



650. A Barktrometer. Used by tanners for ascertaining 

 the density of bark liquor. Dring and Faae. 



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

 the sliding rule accompanying the instrument enables indications at higher or 

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



651. A Small Barktrometer. Dring and Fage. 



The same in principle as the larger one, only not capable of indicating over 

 so -wide a range of gravities. 



