23 



Ordinary Meeting, December llth, 1860. 

 Dr. J. P. Joule, President, in the Chair. 



Dr. Fairbairn brought before the meeting four specimens 

 of Submarine Telegraphic Cable, as constructed by Messrs. 

 Hall and Wells. This cable has a copper wire insulated by 

 India rubber in the centre for the transmission of the electric 

 current. Outside of this are twenty longitudinal strands of 

 hemp steeped in pitch and cork dust, and eight steel wires 

 braided together with twenty-four strands of hemp saturated 

 with Stockholm tar. The specific gravity of the cable in sea 

 water is 1.4 and its weight in air 0.82 ton per mile. 

 The length that would break with its own weight when sus- 

 pended in sea water is 10,810 fathoms; its tensile strength 

 being 2.875 tons. Dr. Fairbairn presented an account of 

 experiments which had been made on the elongation of a 

 sample of the cable twenty feet long by the application of 

 different tensile forces. With a force of 4,480 lbs. there was 

 an elongation of half-an-inch, and after the weight had been 

 removed the cable was found to be permanently stretched 

 1^6 ths of an inch. With a force of 6,440 lbs. the cable broke 

 after having stretched ly^ inches. 



Professor Roscoe explained the recent discoveries by 

 Bunsen and KirchofF of the lines in the spectrum produced by 

 various substances when ignited in the flame of a laboratory 

 lamp. He exhibited beautiful chromo-lithographic drawings 

 of the spectra produced by lithia and various other earths 

 and alkalis. Lithia, which had formerly been supposed to be 

 a very rare earth, was by this means proved to be one of those 

 most extensively distributed. Professor Roscoe stated that 

 Bunsen had, by this new and most delicate system of analysis, 

 been led to the discovery of a new metal which was present 

 in a mineral spring in so small a quantity that twenty tons 

 had to be boiled down to obtain 250 grains of the metal. 

 Proctbedixgs— Lit. & Phil. Society— Xo. 6.— Skssiox, 1880-6L 



