Thermal Badiatiofi in Ahsohtte Measiore. 



269 



I. " On the Eetinal Currents of the Frog's Eye, excited by Light and 

 excited Electrically." By A. D. Waller, M.D., F.KS. 



II. "Observations on the Electromotive Phenomena of Non-medul- 

 lated Nerve." By Miss S. C. M. Sowton. Communicated by 

 Dr. Waller, F.RS. 



III. "Variation." By Professor J. C. Ewart, F.RS. 



'IV. Certain Laws of Variation." By Dr. H. M. Vernon. Communi- 

 cated by Professor Lankester, F.E.S. 



V. "Data for the Problem of Evolution in Man. IV. Note on the 

 Effect of Fertility depending on Homogamy." By Professor 

 Karl Pearson, F.E.S. 



VI. " Mathematical Contributions to the Theory of Evolution. VII. 



On the Inheritance of Characters not capable of Exact Quanti- 

 tative Measurement." (Ee vised.) By Karl Pearson, F.E.S. 



" Thermal Eadiation in Absolute Measure." By J. T. Bottomley, 

 M.A., D.Sc., F.E.S., and J. C. Beattie, D.Sc, F.E.S.E. Ee- 

 ceived November 28, 1899,— Bead February 1, 1900. 



The experiments'^ described in the following paper form a continua- 

 tion of researches on thermal radiation by one of the present authors, 

 the results of which have been communicated to the Eoyal Society 

 from time to time since 1884.t The main object of the present experi- 

 ments was to push forward the inquiry as to the amount, and the 

 relative quality, of the radiation from surfaces of various kinds in high 

 vacuum. 



When a body is maintained at a high temperature the total radiation 

 from its surface depends, other things being the same, on the tempera- 

 ture and on the character of the radiating surface. With a given 

 temperature the total radiation, consisting of thermal, luminous, and 

 iictinic rays, seems to depend on the nature and on the ultimate texture 

 of the radiating surface; and the proportion in which vibrations of 

 longer and shorter period are present seems to be governed by the 



* The experimental results of the paper were obtained two years ago. Various 

 circumstances have prevented earlier publication ; and it was originally intended 

 to carry tlie investigation further before publishing. Want of opportunity, how- 

 ever, makes this difficult for the present; and we therefoi*e deem it advisable to put 

 our results on record just now, as they stand. The present investigation, as well 

 as the former work referred to in the text above, has been assisted by grants from 

 the Government Grant Fund. 



t " On Thermal Radiation in Absolute Measure," J. T. Bottomley, * Roy. Soe. 

 Proc' and ' PhiL Trans.,' 1884— 1893. 



Y 2 



