EXPERIMENTS ON KAOLINIZATION. 



299 



Material experimented upon. — TliG rock Selected by Ml". Beckei' for these exper- 

 iments was the fresliest diabase encountered in the mines. The feldspars 

 show scarcely^ a trace of decomposition, and a large part of the augite is 

 unaltered. It was collected in the Sutro Tunnel, close to the hanging wall 

 of the Lode in the Savage claim. The same rock is described in Chapter 

 III., slide 18, and its analysis is given in the table following page 151 



Results. — The results are reported chronologically, but with all correc- 

 tions, including those based on subsequent experiments. Temperatures are 

 given throughout in degrees centigrade, electromotive forces in volts. 



From an inspection of the tables containing the results for the variation 

 of the electromotive forces of bismuth-silver and bismuth-platinum with 

 temperature, it will be seen that the relation is in both cases so nearly 

 linear that it may at once be assumed as such. One constant, a, only, 

 therefore, results from the calculation. Tables I. and II. contain the data 

 for the calculation of the thermo-electinc constant a for the triple element 

 bismuth-silver, together with the results obtained. Tis the temperature of 

 the warmer, t of the colder end of the element, e the electromotive force 

 corresponding to the temperatures of the respective observations observed 

 or calculated as specified, 6(e) finally the difference between observed and 

 calculated results. Two sets of observations were made in order to ascer- 

 tain to what extent a fixed value for a could be presumed — the bismuth bars 

 being cast and not pressed. In the calculations preference was given to 

 values of e corresponding to greater diff"erences of temperature. 



Table I. 



