DISCOURSE OF W. B. TAYLOR. S21 



Henry showed by experiment, that ice could be employed both 

 as a convex lens for converging heat to a focus, and also as a con- 

 cave mirror for the same purpose: a considerable portion of the 

 incident rays being transmitted, a large portion reflected, and the 

 remainder (a much smaller quantity) absorbed by the ice. 



In 1849, for the purpose of estimating the effects of certain 

 meteorological conditions of the atmosphere, he made some experi- 

 ments on the lateral radiation from a current of ascending heated air 

 at different distances above the flame; the latter being thoroughly 

 eclipsed. 



He also experimented on the radiation of heat from a hydrogen 

 flame, which was shown to be quite small, notwithstanding the high 

 temperature of the flame. By placing an infusible and incombus- 

 tible solid in the flame, while the temperature is much reduced, the 

 radiant light and heat are greatly increased:* results closely 

 analogous to those obtained by him in the differences between the 

 audibility of vibrating tuning-forks when suspended by a soft thread, 

 or when rigidly attached to a sounding-board. These results have 

 also an undoubted significance with regard to celestial radiations; 

 not only as to the differences between gaseous nebulae and stars or 

 clusters, but as to the differences between stars in a probably differ- 

 ent state of condensation or of specific gravity. 



A few years later, he continued his investigation of this subject 

 of radiation, more especially with reference to Rumford's "Obser- 

 vations relative to the means of increasing the quantities of Heat 

 obtained in the Combustion of Fuel :" published in Great Britain in 

 1802.f He found that Rumford's recommendation of the intro- 

 duction of balls of clay or of fire brick (about two and a half 

 inches in diameter) into a coal fire, was fully justified as an eco- 

 nomic measure : more heat being thereby radiated from the fire into 

 the room, and less being carried up the flue. He also showed 

 however that for culinary purposes, while the incandescent or 

 heated clay increases the radiation, and thereby improves the 

 quality of the fire for roasting, it correspondingly expends the tem- 

 perature, and thereby diminishes its power for boiling. " That a 



* Proceed. Am. Phil. Soc. Oct. 19, 1849, vol. v. p. 108. 

 f Journal Royal Institution, 1802, vol. i. p. 28. 

 21 



