[ 229 ] 
Vr. On. the Heat Dissipated hij a Platinum Surface at Hicfh Temperatures. 
Part IV. Thermal Emissivity in High-pressure Gases. 
By J. E. Petavel, A.M. hist. C.E., A.M. Inst. E.E., Past 1851 Exhibition Scholar, 
John Harling Felloiv of the Owens College, Manchester. 
Communicated by Arthur Schuster, F.R.S. 
Received Felimary 7,—Read March 7, 1901. 
Contexts. 
Introduction. 
Apparatus. 
Experimental "Work. 
Causes of Error. 
Results obtained. 
On the Variation of Emissivity with Pressure. 
An Analytical Study of the Total Heat Dissipated. 
Some Experiments on the Loss of Heat by Convection. 
On the Influence of Experimental Conditions . .. 
The Dimensions of the Radiator. 
The Dimensions of the Enclosure. 
The Temperature of the Gas. 
Average Temperature of the Gas. 
A Numerical Comparison of the Heat dissipated by Conductivity in Solids and 
Emissivity in Gases. 
Explosive Properties of Nitrous Oxide. 
Emissivity in Licpiid Gases. 
Conclusions. 
I’age 
229 
230 
232 
233 
234 
237 
239 
243 
243 
244 
244 
245 
245 
246 
246 
247 
247 
PART IV.* 
Thermal Emissivity in High-pressure Gases. 
The question of tlie heat dissipated a hot Ijody in gases at ordinary pressures 
1ms received consideralde attention during recent years. The subject has Imen 
* For Parts I., IL, HI. see ‘Philosophical Transactions of the Royal Society,’ A, vol. 191, p. 501, 1898. 
Part I. was entitled “ Emissivity of a Bright Platinum Surface in Air and other Gases.” 
Part H. ,, “ A Bolometric Study of the Law of Thermal Radiation.” 
Part HI. ,, “On the Variation of the Intrinsic Brilliancy of Platinum with Temperature.” 
(292) 23.10.1901 
