PHYSICS. 353 



sou, aud Youug are to the same purpose. {Nature, 1881 , xxiii, 264, 288, 

 341, 383, 504 ; xxiv, 4, 28, 77, 113, 1G7, 239 ; Ber. Berl. Chem. Ges., April, 

 1881, xiv, 718.) 



Chaudler Eoberts aud Wrightsou have determined the deusity of 

 melted bismuth by means of the oncosimeter, an instrument devised by 

 the latter gentleman. It is composed of a ball of the metal whose den- 

 sity in the melted state is to be studied, or of a metal less fusible. It is 

 suspended at the extremity of a spring and is completely immersed in 

 the fused metal. The difference, either positive or negative, between its 

 weight and the upward pressure when in the liquid is measured by the 

 lengthening or shortening of the spring, and is registered by a lever on 

 a rotating cylinder. The value of this difference at the moment of im- 

 mersion, before the ball has had time to heat, gives data for the calcu- 

 lation of the specific gravity of the liquid, that of the ball having been 

 determined. The authors find for the specific gravity of melted bismuth 

 10.055, that of solid bismuth being 9.82; for iron in fusion 6.84; in the 

 pasty state 6.33; and cold 6.95. {Phil. Mag., April, 1881, V. xi, 295.) 



Nies and Winkelmann have investigated the volume changes of vari- 

 ous metals in solidifying. Of eight metals examined, six, viz, tin, zinc, 

 bismuth, antimony, iron, and copper, were proved to undergo expansion 

 in passing from the liquid to the solid state. For three of the metals 

 approximate values for the amount of this expansion were obtained. 

 Tin showed an expansion of 0.7 per cent., zinc 0.2, and bismuth 3. Two 

 metals, lead and cadmium, gave doubtful results. The authors have 

 reason to believe that they also expand in solidifying. If this be so, 

 the rule would api)ear to be a general one for the metals. {Nature, April, 

 1881, xxiii, 616.) 



Fornioni has described an evaporimeter with constant level. It con- 

 sists of an oblong wooden case with a brass spiral descending into it 

 from a micrometric screw. The spiral, carries at its lower end a small 

 glass vessel, which acts as feeder. A glass siphon extends outward 

 horizontally from the feeder and has at its outer end a small cup in 

 which the evaporation takes place. As the water evaporates in the cup 

 the feeder is lightened and rises by the action of the spiral, thus keep- 

 ing the level constant. A fiue layer of oil in the feeder prevents evapo- 

 ration from its water-surface. There are guides to control the vertical 

 movements of the feeder, which moreover are indicated by means of a 

 weighted thread affecting an external index on a disk. The gradua- 

 tion of the instrument is expressed in millimeters of the height of water 

 in the evaporating vessel. {Nature, August, 1881, xxiv, 387.) 



Van der Mensbrugghe has calculated that if evaporation subdivides 

 the liquid of seas into spherules of, say, yowo millimeter in diameter, 

 each kilogram of water presents a collection of spherules whose total 

 potential energy is equivalent to 450 kilogram-meters, i. e., more than 

 a million times that of a sphere of compact water also weighing a kilo- 

 S. Mis. 100 23 



