PHYSICS. L) < 5 



MECHANICS. 

 1. Of Solids. 



Kalischer has studied the molecular structure of metals by removing 

 the surface by means of a suitable liquid. The crystalline structure 

 is generally developed in this way; though sometimes an electrolytic 

 current is necessary, the metal being made the positive electrode. It 

 appears from these experiments that nearly all the metals have a crys- 

 talline structure, but that mechanical treatment in general causes this 

 structure to disappear. Heat, however, causes a return to the crystal- 

 line condition. Hence the explanation of the increase of conducting 

 power in metals by the process of annealing. (J. Phys., June, 1883, II, 

 II, 285.) 



The publications of the Vega expedition contain a memoir by Petter- 

 son on the properties of water and ice, in which the discovery is an- 

 nounced that in the vicinity of the melting point the volume of ice de- 

 creases as the temperature rises. With the purest distilled water, the 

 ice did not begin to contract till the temperature rose to — 0.03° C. With 

 ice made from water from the laboratory stone jar, the contraction be- 

 gan at —0.3° C. With sea-water of specific gravity of 1.0003, contain- 

 ing — 0.014 per cent, of chlorine, the ice began to contract at — 4° 

 C. ; with that of 1.00534 gravity and 0.373 per cent, chlorine, the con- 

 traction began at — 14° C. ; and with that of 1.0094 and 0.049 of chlo- 

 rine, it began to contract at —19° O. Moreover, the author finds 

 that sea-water ice contains more sulphates, the brine more chlorides, 

 than the sea-water itself. (Nature, August, 1883, xxviii, 417.) 



2. Of Liquids. 



The experiments upon the compressibility of liquids thus far made 

 go to show that water is an exception to the general law that the coeffi- 

 cient of compressibility increases with the temperature. The most ac- 

 curate of these experiments, however, those of Grassi, were made at 

 temperatures below 53°.3 C. Pagliani and Vicentiui have repeated 

 these experiments, using distilled and recently boiled water, and ex- 

 tending the temperature to 100°. They have reached the interesting 

 result that between 0° and 55° the coefficient decreases as the tempera- 

 ture rises, as Grassi had observed; but that between 55° and 100°, it 

 increases with the temperature, like that of other liquids. Hence a tem- 

 perature exists for which the compressibility has a maximum value. 

 (J. Phys., October, 1883, II, n, 401.) 



Volkmann draws the following conclusions from his experiments on the 

 cohesion of saline solutions : (1) The cohesion, or the superficial tension, 

 is modified only very slightly by traces of impurities; (2) the specific 

 cohesion of a saline solution diminishes generally as the amount of the 

 salt present increases, the capillary constant proportionally increasing; 



