02 H-FECTS or CLOTHTKG, &C. 



By applying thefe refults to the numbers in Exp. 11. where 

 the cooling was efFedled in 36^ minutes, the Count fays as 53| 

 minutes give 2985 heat pafled through the covered ends, fo 

 will 36-5- minutes give 1942 parts. And this taken from 10000, 

 the whole heat loft, will leave 8058 for the heat that really 

 Whence the pafled through the upright fides. But it was found that 7015 

 xeAiits^arccor- ^^^^ through, the naked fides in 551 minutes: Whence 

 7015 : 551 : : 8058 : es^. And confequently, the correded 

 times are 36|- and 63^, which exprefs the velocities of the 

 pafTage of heat through the furface of the naked metal, and 

 that which was blackened with fmoke, viz. as 5654 to 10000 

 nearly. 



In the fame manner the velocities of the paffage of heat in 

 the experiment No. 6. ar« (hewn to have been as 4566 to 

 10000. 

 A ncwcoitffeof It has been remarked that, in thefe curious inftances of the 

 experiments. effeds of modification of furface or clothing upon the tran- 

 fitions of heat, the effed may have been favoured by commu- 

 nication to the air, or by facilitating the procefs of radiation^ 

 The author's reafoning upon Exp. 2. appeared not fo decifive 

 as to need no fapport from experiments of a different clafs. 

 He therefore conftru6ted an inftrument for meafuring the efFecls 

 of radiation, which is leea in Fig. 2, Plntel. 

 Inftruments for Like the hygrometer of Mr. Leflie,* (as the Count ob- 

 improvingradi- ferves) it confifts of two glafs balls at the ends of a tube C 

 **' ^^' and E. The tube is of fuch a diameter that one inch in length 



*vould contain 15 grains of mercury; the balls are 1.625 

 inches in diameter; the upright ends of the tube C and E are 

 each 10 inches long; the horizontal part D Is 17 inches; and 

 the board A B, to which it is attached, is 27 inches long, 9 

 inches wide, and one inch thick. The pillar F fupports a cir- 

 cular vertical fcreen made of pafteboard, covered with gilt 

 paper on both fides, the ufe of which is to protect one of the 

 balls from rays intended only to act upon the other. The balls 

 contain only air, and a fmall drop of coloured fpirit of v/ine 

 is introduced by means of a (liort tube proje61ing from one of 

 the elbow s ; which Ihort tube is then hermetically fealed. By a 

 little management the bubble of fpirit is brought to reft in the 

 middle of the horizontal tube; and when the temperature of 

 * 



• Philofophlcal Journal, quarto feries, lU. 4 61. 



the 



