256 fROCfiEDINGS Of SECTION A. 



We find such in Siberia, where in some places the difiterence 

 between the lowest winter temperature and the highest 

 summer temperature is as much as 150 degrees Fahr. The 

 astronomical theory is here ]>roperl)^ exhibited. 



Finally, the astronomical doctrine demonstrates that 

 vast climatic changes must have taken place at remote 

 periods in the earth's history, so that even if geologists had 

 not already discovered traces of glacial periods, the mathe- 

 maticians would have known that they must have existed, 

 and would be urging the geologists now to find them. 



2._0N THE CONDUCTIVITY OF SOLUTIONS OF 

 COPPER SULPHATE. 



Bu W. H. STEELE. 

 \^ Abstract, A^ 

 The following results were obtained from a very great 

 number of observations on solutions of various concentrations 

 of pure copper sulphate (CaSO^ +5H2O). Kohlrausch's 

 method of measuring the resistances was employed. 



I. Effect of change of temperature on conductivity. The 

 cell used was a glass tube about 1 cm. in diameter and 

 20 cms. in length, with each end fitting into necks in the 

 sides of copper cups, whose inner surfaces were the electrodes 

 with areas of about 80 sq. cms. These cups were closed at 

 the. top with blocks of india-rubber and connected with 

 Liebig condensers. If R be the resistance of the cell when 

 filled with the solution and o- be the specific resistance, R 



= — o- where 7 is the mean radius and I is the length 



Try 

 increased by "87 at each end. The conductivity k is the 



reciprocal of (t, and — is a constant determined once for all 



# 1 



bv measurement ; its logarithm is 1*2540. Thus k = ^ 



'' 7r7 it 



and log K = 1*2540 — log R, so that the calculation of k 



from observed value R is simple. From the observations I 



had first to find the law of variation with temperature, and 



secondly, the variation with concentration. The former is 



given approximately by Kt — Kg^ (1 + at — (5t% where I 



have taken 20° C. as standard and t the excess of the temp. 



C. over 20°. I find the mean value of a = *0229, (5 = 



