ABSTRACTS OF SCIENTIFIC PAPERS. 



I. On Gutta-Percha as an Insulator at various Temperatures. ' British 



Association Keport for 1859,' p. 248. 



II. On t/i.^ Instilfiting Properties of Gutta-Percha. 'Proceedings of 



the Royal Society,' 1860, vol. x. p. 409. 



These papers contain abstracts of experiments made at the works 

 of Messrs. R. S. Xewall and Co.. to determine in absolute measure 

 the insulation resistance of the gutta-percha coating of submarine 

 cables, and the effect of temperature on that resistance. The author 

 draws attention to the phenomenon of 'polarisation' or the apparent 

 increase which the resistance of the insulator undergoes for some time 

 after the application of the testing battery. Tables are given show- 

 ing the specific resistance of the gutta-percha used in the Red Sea 

 Cable after one and after five minutes' electrification ; also of the 

 specific resistance of pure gutta-percha, at temperatures ranging 

 from 50 to 80 Fahrenheit. 



[An account of the same experiments was printed as an Appendix 

 to the Report of the Committee on Submarine Cables, 1859, in 

 connection with evidence submitted to the Committee by Professor 

 Jenkin.] 



III. On Permanent Thermoelectric Currents in Circuits of one Metal. 

 'British Association Report for 1861,' p. 39 ; 'Chemical News,' 

 October 26, 1861, vol. iv. p. 222. 



After referring to experiments by Seebeck and Magnus, on the 

 production of transient thermoelectric currents in circuits of one 

 metal by bringing together cold and hot ends of a wire, the author 

 announces the discovery that he had obtained permanent currents 

 by looping the two ends of a wire together and heating one of the 

 two loops, and that these currents were usually much greater when 

 there was a loose contact between the wires than when the loops 

 were tightly drawn together. He first observed that if one loop 

 was heated when both were held tightly together, and then the loops 



