[BARNES] THE PHYSICAL CONSTANTS OF ICE 11 



On account of its importance in meteorology, the conductivity of 

 snow has received a great deal of attention. 



Andrews, in 1885, determined the relative conductivity of ice and 

 snow and found that of ice to be about 122 per cent greater than that of 

 snow. In 1889, Hjeltstrom determined the conductivity by burying 

 four thermometers, at different depths; and obser\ed the temperature 

 with great care from time to time. Taking the specific heat of snow as 

 0.50 and the density as 0.183, he found as a mean the value .000507 

 in C. G. S. units. 



In 1891 Abels found that the conductivity was proportional to the 

 square of the density of the snow, or that K^.00677D- in C. G. S. 

 units. 



Jansson, in 1901, determined the conductivity of snow by consider- 

 ing it as a fine powder and applying a method which had been worked 

 out by Christiansen in 1881. The snow was placed between three cir- 

 cular copper plates into which thermo-junctions were inserted. The 

 outer plates were maintained at the required temperatures in order to 

 cause a measurable flow of heat across the snow. It was found that the 

 conductivity K could be represented by the following expression. 



K= .00005 + .0019d -\- .OOed^ 



in C. G. S. units, where d is the density of the snow. It was further 

 found by Jansson that the conductivity depended on the form and size 

 of the crystals. 



In 1905 Okada published the results of a careful series of measure- 

 ments. He found that the density of snow varied with the depth ac- 

 cording to the following order 



at 5 cm. 0.13 



25 cm. 0.24 



34 cm. 0.29 



45 cm. 0.35 



Between 10 and 20 cms. the conductivity was found to be .00028, 

 while for a depth of 20 to 30 cms. the value of K was . 00045 in C. G. S. 

 units. These results were found to agree with Abels' formula, which 

 gives for the density determined by Okada the value, in one case of 

 .00022, and in the other the value .00039. The formula of Jansson is 

 not in such good accord. 



Coefficient of Expansion of Ice. 



The earliest determinations of the coefficient of expansion of ice 

 were made by Brunner in 1845, who obtained .0001125; by Struve, in 



