250 



REPORT — 1859. 



The specific resistance of gutta percha of the Red Sea core, at 6°Fahrenheit, calcu- 

 lated from daily tests of the Red Sea cables, was found to be 205 X10 18 absolute 

 British units. 



Owing to the influence of the phenomenon of extra resistance described above, this 

 number does not express a well-defined resistance such as that of a metal, but gives 

 an approximate resistance at about thirty seconds after application of the battery. 



The corresponding specific resistance at 60° of No. 1 coil was found to be 195 X 10 1 *. 



The specific resistance of No. 2 coil at the same temperature was 202 X 10 ls . 



The resistance at other temperatures, or after longer application of the battery, is 

 inversely proportional to the numbers given in the three Tables, and representing 

 the relative loss. 



The employment of Chatterton's compound in different proportions from those 

 used in the above coils, would necessitate fresh experiments in each case to determine 

 the effect of temperature. 



Since writing the above paper a detailed account of the experiments, and the results 

 of more extended calculations, have been communicated to the Royal Society in a 

 paper read March 22, I860. 



Table I. 



Table II. 



Table III. 



