148 SEC. 5. MOLECULAR PHYSICS. 



The areometers constructed by the exhibitor, the normal weight of which 

 has been recommended by Mr. Hirsch, apothecary, at Giessen, and which 

 corresponds to the gram scale, have the following advantages, compared with 

 other similar instruments : 



They can be easily tested as to their accuracy (as shown before) ; they 

 will not be affected by the liquids ; they can be easily cleaned, and will 

 sink slowly and uniformly in any liquid, and are not surpassed, not even 

 equalled, by most similar instruments, in respect of accuracy. 



One of the exhibited areometer-cases contains three spindles, which are 

 perfectly equal in point of accuracy with those in the second case. The 

 milky glass lines at the neck are, however, fastened only with sealing-wax, 

 which, in case of great carelessness, may dissolve, although persons of ex- 

 perience have used these spindles for years without injury ; besides, every 

 particle of sealing-wax can be easily supplied as soon as any defect has been 

 noticed. But, in order to avoid this, the milky glass lines on the three 

 Bpindles in the second case have been melted together with the glass 

 plate. 



Besides the weights, there are added to the two cases a cylinder for 

 weighing the liquids, a pincette for placing the weights, and a thermometer 

 for determining the temperature of the liquids, which latter, by reason of its 

 form and the strength of the glass, is at the same time to be used as a stirring 

 rod. 



The exactness of the indications of Zorn's spindles affords also the advant- 

 age of testing the correctness of other liquid scales, such as Tralles, Baume, 

 and others made on a scientific basis. 



679. Alcohol-meter. 



Siemens Brothers and Co., Charlottenburg. 



679a. Metallic Alcoholometer, on Tralles's principle. 



W. Gloukhoff, St. Petersburg. 



The metallic alcoholometer, with additional weights, newly adapted by the 

 Russian Government. This alcoholometer is made on the principle of Sykes's 

 hydrometer, but its scale is adapted to the system of Tralles, legalized in 

 Russia. 



VI. MISCELLANEOUS. 



680. Apparatus, serving to illustrate the Mechanical 

 Effect of the Expansion of Liquids. T. A. Snyders, Delft. 



Gun-tubes closed by lead plate 3 millimetres thick, which is maintained 

 by an annular screw-piece. The expansion of the liquid causes a disc of lead 

 to be drawn out with a crack through the hole of the screw-piece. 



681. Apparatus, constructed by Leschot and Thury, to 



suppress Friction by the interposition of a stratum of air. 



Geneva Association for Constructing Scientific Instru- 

 ments. 



