fhe explanation is that the ice in the former ease was melted by the 

 heat conducted from the air. {Nature, May, 1883, xxviii, 47.) 



Forel bas sought to explain the granulation of glaciers by the alter- 

 nate action of heat and cold to which they are annually subjected, 

 without the intervention of any exterior pressure whatever. Hagen- 

 bach, on the contrary, suggests that if it is legitimate to suppose that 

 the pressure required to lower the temperature of fusion by a definite 

 amount, say 0.01°, is a function of its direction relative to the crystal- 

 line axis, i. e., that it is less perpendicular to the optic axis than parallel 

 to it, then it follows that two crystals of ice with their axes perpen- 

 dicular would undergo fusion by pressure in different degrees, the water 

 from the fusion of the one serving to increase the volume of the other. 

 Hence he believes that pressure exerts the preponderating influence on 

 the phenomenon, the variations of temperature playing only a second- 

 ary part. (Arch. Gendve, vn, 329 ; vm, 343 ; J. Phys., August, 1883, 

 II, II, 377.) 



Crova has devised an improved form of condensation hygrometer, 

 consisting of a thin brass tube, nickel-plated and carefully polished in 

 its interior, closed at one end by a plate of ground glass and at the 

 other by a lens of long focus. This tube is fixed in a closed rectangular 

 metal box, furnished with two stopcocks. This box is two-thirds filled 

 with carbon disulphide and air is blown through it, producing cold by 

 its evaporation. A gentle current of the air to be tested is drawn 

 through the tube, and when dew appears on the polished surface the 

 temperature is noted on a thermometer in contact with the tube. The 

 cooling current is then stopped and the temperature again noted at the 

 instant when the dew disappears. The author claims tlftit the dew 

 point may be determined to 0°.l. (J. Phys., April, 1883, II, II, 166.) 



In a subsequent paper, Crova gives the results of his experiments 

 made to compare the accuracy of the above interior condensing hy- 

 grometer with the ordinary exterior coudensing instrument and with 

 the psychrometer. The maximum differences between the two former 

 instruments were obtained when the relative humidity was low and 

 the wind from north to northwest. The minimum differences were 

 observed when the relative humidity was high and the wind from the 

 south and slight. The psychrometer differed notably and in most cases 

 arbitrarily from the other instruments. (J. Phys., October, 1883, II, n, 

 450.) 



According to Hutton's theory, rain is produced by the mixture of 

 two masses of saturated air at different temperatures. Pernter has 

 sought to test the theory by calculating the quantity of rain produced by 

 mixing two given masses of air at given temperatures. He finds that 

 to produce upon one square meter a rainfall of 1 millimeter it is neces- 

 sary to mix in a very short time 685 cubic meters of saturated air, one- 

 half of which is at 0° and the other at 25°, the pressure being 760 mm 

 throughout the mass. If, therefore, any rain can be produced on Hut- 



