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XII. On the Heal Dissipated by a Platinum Surface at High Temperatures. 



By J. E. PETAVEL, 1851 Exhibition Scholar. 



Communicated by Lord RAYLEIGH, F. R.S. 



Received May 19, Bead June 9, 1898. 



[PLATES 18-23.] 



FROM the beginning of the century, and more especially of late years, an almost 

 uninterrupted series of papers have appeared on the above subject. Unfortunately 

 few of the authors have reduced their measurements to absolute units, thus rendering 

 comparison of the results obtained very difficult. 



The first part of this paper is to some degree an extension to higher temperatures 

 and pressures of the work so ably done by Dr. BOTTOMLEY,* whilst the names of 

 LANGLEY, PASCHEN,t WEBER, J and many others will occur to anyone glancing 

 through the second and third parts. 



With regard to temperature measurements, the present work is mainly founded on 

 the researches of CALLENDAR and GRIFFITHS, which have been amply confirmed by 

 the later investigations of HEYCOCK and NEVILLE. || 



Full references to the above papers are given here once for all, as we shall have 

 continually occasion to refer to one or other of them. 



On the Apparatus Employed. 



The preliminary experiments soon showed that to obtain reliable results a very 

 thick wire must be used for the double purpose of radiator and thermometer, even 

 if it were at the cost of a slight loss of sensitiveness, the reasons being the 

 following : 



* ' Phil. Trans.,' A, vol. 178, 1887, p. 429, and 'Phil. Trans.,' A, vol. 184, 1893, p. 593. 



f ' Wied. Ann.,' vol. 49, p. 50, 1893 ; vol. 58, p. 455, 1896, and vol. 60, p. 663, 1897. 



| ' Physical Review,' vol. 2, p. 112; ' Berichte der Preussischen Akademie,' 1888, p. 933, &c. 



' Phil. Trans.,' A, vol. 182, p. 119, 1891. 



|| ' Journ. of the Chem. Soc.,' vol. 67, p. 160, 1895 ; same vol., p. 1024; ' Phil. Trans.,' A, vol. 189, 

 p. 25, 1897. On this subject see also C. M. CLAKKE, ' The Electrician,' vol. 38, pp. 175, 241, 372, and 

 J. D. H. DICKSON, ' Phil. Mag.,' December, 1897, p. 445. 



25.10.98. 



