REPORTS ON THE STATE OF KNOWLEDGE OF RADIANT 

 HEAT, MADE TO THE BRITISH ASSOCIATION FOR THE 

 ADVANCEMENT OF SCIENCE, AT THE MEETINGS IN 1832, 

 1840, AND 1854. 



By the Reverend Badbn Powell, M. A., F. R. S , Savilian Professor of Geometry in the 



University of Oxford. iS 



REPORT FOR 1832. 



In attempting to give a condensed account of the present state of 

 our knowledge of the science of Radiant Heat, it appears to me that 

 I shall be best consulting the design of such a report by offering, in 

 as brief a form as possible, a sketch of what has been formerly done 

 in this department ; and thence proceeding to a more detailed sur- 

 vey of what is now doing. And we shall proceed with greater clear- 

 ness if we distinguish the several different departments into which 

 the subject divides itself, agreeably to certain known distinctions in 

 the properties and species of heat acting under peculiar circumstances. 

 All these have been too commonly confounded together under the 

 general and vague name of Radiant Heat, whence not unfrequently 

 the most erroneous views have resulted. By distributing our sub- 

 ject, however, under the few well-marked divisions which the scanty 

 results of observation as yet supply, we shall at once secure perspi- 

 cuity in our views, and be treating the subject in a way most accord- 

 ant with the inductive process : which, it must be distinctly avowed, 

 has not yet enabled us to advance to any such comprehensive knowl- 

 edge of the facts as can warrant us in generalizing them, or in 

 ascribing to a common principle the radiation of heat from a mass of 

 hot water, from aflame, and from the sun. 



We shall take each of these principal divisions separately, and 

 under each shall consider what is known in reference to those prop- 

 erties to which experiment has been directed. 



Division I. 



Radiation of heat from hot bodies below the temperature of lumin- 

 osity. 



" We regret to state that since the date of the present Report of the Smithsonian Insti- 

 tution, we have received intelligence of the death of the gifted author of these admirable 

 articles. In his departure from this life science has been called to mourn a successful and 

 industrious investigator, an able defender, and an accomplished expounder of her princi- 

 ples. As a scholar, a writer, and a christian gentleman, we can but seldom hope to look 

 upon his like again. The republication and wide diffusion of these reports, in a collected 

 form, will, we trust, be considered of importance in the advance of science, and we hope 

 to be able to publish a continuation of them by some worthy successor of Professor Powell. 



J. H. 



