﻿934 



Mr. A. H. Davis on Natural 



showing the relation between the linear emissivity H of the 

 wire in cals. per cm. length per degree temperature excess, 

 and the temperature excess 0. 



(a) Representation hi the form H/k= F(e 2 gd 3 a9 / k 2 )f(cvj k) . 



In Table IV. these results are represented in the form 

 showing the relation to the equation for inviscid fluids, 

 and H/k is given for various values of (c 2 gd d a6/k 2 ), the value 

 of cv/k for the liquid being stated. The heat losses obtained 

 for jiir do not appear in this table as they fall under very 

 much smaller values of (gd d a0c 2 /k 2 ). 



Table IV. 

 Relation between H/k and gd 3 ac 2 6/k 2 . 













gd*ac 2 0k 2 





Liquid. 



cv/k. 



Wire 

 diarn. 











1. 

 25 



2. 



2-6 



5. 



30 

 2-9 



10. 



3-2 



3-2 



20. 



3-5 

 36 



50. 



4-1 

 4-1 



100. 



4-7 

 4-6 



200. 



Toluene 



7-2 



0-0083 

 00155 



CC1 4 



8-0 



00083 

 0-0155 



2-3 



2-6 



2-9 



3-2 

 32 



3 5 

 3-6 



40 

 4-2 



4-7 



5-2 





Aniline 



69 



0-0083 

 00155 



1-9 



22 



2-5 

 2-5 



28 



2-7 



32 



3-0 



3-8 

 3-5 



43 

 40 



4-6 



Olive oil ... 



1400 



0-0083 

 00155 



14 



1-6 



1-8 

 1-7 



2-0 

 1-9 



21 

 2-1 



2-4 



2-8 



33 



Glycerine... 



7640 



00083 

 0-0155 



1-4 



1-4 



1-5 

 1-4 



1-7 

 1-5 



1-7 



2-0 



2-4 





It is clear from the table that for a given liquid the 

 relation between ~K/k and c 2 gd z a6jk 2 is practically independent 

 of the diameter of the wire. 



There appears, however, to be a tendency for the finer 

 wire to give values of H/& a few per cent, higher than the 

 other, and this is most probably due to the temperature 

 variation of the properties of the fluids for which no 

 allowance has been made. 



In considering the cooling of the wires in gases, where 

 much greater temperature excesses were involved, it was 

 found that approximate allowance of this kind corrected a 

 similar tendency*. It appears on approximate calculation 

 from what data are available (mainly temperature coeffi- 

 cients of viscosity) that in the present experiments the 

 * Davis, Phil. Mag. xliii. p. 329 (1922). 



