BIBLIOGRAPHY OF IIERSCIIEL's WRITINGS. 575 



Herschel, W.: Synopsis of the Witrrixtis of— Continued. 



A. D. Vol. r. 



1800 90 462-4()3 Description of apparatus used. 



464-470 Experiments 63 to 93. Transmission of lieat from a candle Hame 

 tlirough the various substances used betore. 



470 TraxsmissioH of the Solar Heat which h of an Equal Hrfranr/ihilily with 

 lied PrwmaUc Bays. 



470-471 Description of apparatus us(^d. 



471-476 Experiments 94 to 116. Transmission of red solar rays tbrougb the 

 substances used before. 



476 Transmission of Fire-Heat through rarions Substances. 



476-477 Description of apparatus. 



477-485 Experiments 117 to 147. Transmission of heat from a grate fire 

 through the same plates before used. 



485 Transmission of the Invisible Eays of Solar Heat. 



485-490 Experiments 148 to 169. 



490 Transmission of Invisible Terrestrial Heat. 



490-492 Method and apparatus employed. 



492-497 Experiments 170 to 194. Transmission of heat from a stove by the 

 plates before used. 



497 Art. VI. Scattering of Solar Heat. 



497-498 Description of apparatus. 



499-506 Experiments 195 to 219. Determinations of the amount of heat 

 scattered l)y various kinds of paper, textile fabrics, metals, &c. 



506 Art. VII. Whether Light and Heat be occasioned by the same or by Differ- 

 ent Bays. 



506 " Before we enter into a discussion of this question it appears to me 

 that we are authorized, by the experiments which have been de- 

 livered in this paper, to make certain conclusions that will entirely 

 alter the form of our enquiry. Thus, from the 18th experiment it 

 appears that 21 degrees of solar heat were given in one minute to 

 a thermometer by rays which had no power of illuminating objects 

 and which could not be rendered visible, notwithstanding they 

 were brought together in the focus of a burning lens. The same 

 has also been proved of terrestial heat iu the 9th experiment, where 

 in one minute 39° of it were given to a thermometer by rays totally 

 invisible, even when condensed by a concave mirror. Henr a it is 

 established, by incontrovertible facts, that there are rays of heat, 

 both solar and terrestrial, not endowed with a power of rendering 

 objects visible. 

 "It has also been proved, by the whole tenour of our prismatic ex- 

 periments, that this invisible heat is continued, from the beginning 

 of the least refrangible rays towards the most refrangible ones in a 

 series of uninterrupted gradation, from a gentle beginning to a 

 certain maximum, and that it afterwards declines as uniformly to 

 a vanishing state. These phenomena have been ascertained by an 

 instrument which, figuratively speaking, we may call blind, and 

 which, therefore, could give us no information about light ; yet, 

 by its faithful report, the thermometer, which is the instrument 

 alluded to, can leave no doubt about the existence of the different 

 degrees of heat in the prismatic spectrum. 

 ''This consideration, as has been observed, must alter the form of 

 our pn)poscd inquiry, for the question being thus at least partly 

 decided, since it is ascertained that we have rays of heat which 

 give no light, it can only become a subject of inquiry whether 



