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Xll — The Absolute Thermal Conductivity of Nickel. By T. C. Baillie, M.A., 

 B.Sc, Assistant Lecturer and Demonstrator in Physics, University College of 

 North Wales, Bangor. (With a Plate.) 



(Read 16th May 1898.) 



§ 1. Introduction. — The experiments described in this paper were commenced with 

 the view, not only of determining the absolute thermal conductivity of nickel, but also 

 of comparing the results found by Forbes's and Angstrom's methods for the same 

 specimen. Although some readings were taken for Angstrom's method, that part of 

 the investigation was not completed, because it was found that the experimental 

 errors — unavoidable, on account of the necessity of measuring rapidly changing 

 temperatures — would be too great for the results to be of any value. The thermal 

 conductivity of a portion of the bar of nickel used for Forbes's method was determined 

 by a direct method involving the determination only of steady temperatures, and the 

 results so obtained are given in the latter portion of this paper. 



Forbes's Method. 



§ 2. The Statical Experiment. — The nickel bar used was kindly lent by Dr Knott, 

 being a piece about four feet long, which he had no immediate occasion to use for his 

 own experiments on " The Strains produced in Iron, Steel, and Nickel Tubes in the Mag- 

 netic Field" (see Trans., vol. xxxviii. part iii. No. 13). This bar was turned down so 

 as to be of uniform circular section, and holes for thermometers were drilled into it by 

 Messrs Aitken & Allan, Edinburgh. Four thermometer holes were drilled in each of 

 the end portions of the bar, so as to leave a length of 19 inches intact for a tube re- 

 quired by Dr Knott at a later period. 



The bar was set up in Professor Tait's private laboratory, with the same fittings, 

 altered to suit the size of the nickel bar, as were used by Professor Tait, and afterwards 

 by Dr Mitchell, in their experiments on thermal conductivities (see Trans., 1878, xxx., 

 and Trans., 1887, xxxiii. part ii. p. 535). One end of the bar was fitted with 

 white lead into a round hole in the side of a cast-iron pot, which was afterwards 

 nearly rilled with solder. This end of the bar was heated by a bunsen flame 

 placed under the pot of solder. A constant temperature was maintained at this 

 end of the bar by keeping the gas supplied to the bunsen burner at constant 

 pressure by means of Professors Tait and Crum Brown's gas regulator. This 

 regulator is like a small gasometer, one of the balancing weights of which, on 

 descending, bends a piece of soft, flexible rubber tubing conducting the gas supply 

 to it, so as to diminish the internal cross-section of the piece of soft tubing ; 



VOL. XXXIX. PART II. (NO. 12). 3 I 



