BIBLIOGKAI'HY OF HERSCIIEL's WHITINGS. 573 



Herschel, "W.: .Synoi-sis of iin; Wuhincs of— Contiimcd. 

 A. D. Vol. P. 



1800 90 :U0 i:Uh ExperiiiH'til. J,', fraction of the I hat that accompauirs the Coloured 

 part of the I'ri.siiKitic ^Spectrum. 

 A burning Urns i) iuchcH iu (liiuiictcr \v:is covered hy a piece of paste- 

 board in which there was an opening of a sufficient size to admit 

 all the colouriHl part of the prismatic spectrum. As the thermom- 

 eter showcHl rise of temperature, the conclusions were, that if the 

 colonred rays themselv(>s are not of a heat-making nature, they are 

 at least accompanied with rays that have the power of heating 

 311 bodies, and that these rays an; subject to certain laws of refraction 



which cannot dilier mntdi from those affecting light. 

 311-312 14th Experiment. Refraction of the heat of a Chimneii Fire. The 



same burning glass before the clear fire of a largt; grate. 

 313-314 l.'jth Experiment. Ihfraciion of the Heat of a Bed-hot Iron. This 



was by a lens of 1.1 inches diameter. 

 315-316 16th Experiment. Hefraction of lire-heat hij an rnsfrnment resem- 

 hVuHj a Telescope. 



317 17th Experiment. Hefraction of the InrisihJe rays of Solar Heat. The 



burning kus of 9 inches diameter was half covered by a screen of 

 pasteboard, upon which the prismatic spectrum was thrown, keep- 

 ing the last visible red colour one-tenth of an iiieh from the edge of 

 the pasteboard. The thermometer, which had its ball at the focus 

 for red rays, showed great increase of temperature; but at the same 

 time exhibited a slight red colouration. This occasioned a surmise 

 that possibly the invisible rays of the sun might become visible, if 

 they were properly condensed. 



318 18th Experiment. Trial to render the Inrisihle Bays of the Sun f'isible 



hy Condensation. 

 The previous exjieriment was modified so that the last visible red 

 colour was two tenths of an inch from the margin of the paste- 

 board. Here a marked increase of temperature was evinced with- 

 out a vestige of light. 



319 19th Experiment. Befraction of Inrisible Culinary Heat. 



A heated cylinder of iron was placed on one side of a lens of 1.1 inches 

 diameter, and the ball of a thermometer in the secondary focus on 

 the other side of the lens. A small pasteboard screen was alternately 

 removed from before the thermometer and replaced, the thermometer 

 exhibiting corresponding rise and fall of temperature, from a bright 

 red. heat of the cylinder down to its weakest state of black heat. 



320-321 20^h Experiment. Confirmation of the Wth. 



322 "As we have now traced the rays which occasion heat, both solar and 

 terrestrial, through all the varieties that were mentioned in the be- 

 ginning of this paper, and have shown that in every state they are 

 subject to the laws of reflection and refraction, it will be easy to per- 

 ceive that I have made good a proof of the first three of my prop- 

 ositions. For the same experinumts which have convinced us that, 

 according to our second and third articles, heat is both rellexible 

 and refrangible, establish also its radiant miture, and thus e(iually 

 prove the first of them." 

 [Dated] Slough, near Windsor, April 2!>, 1800. 



323-326 Explanation of the Figures. Plates XII, XII, XIV, XV, and XVI. 



1800 90 437 Experiments on the Solar and on the Terrestrial Bays that occasion Heat; 



icith a comparative View of the Laws to ivhich Light and Heat, or rather 



the Bays ivhich occasion them, are subject, in order to determine whether 



