EFFECTS OF CXOTHING, &C. jS\ 



was covered by one or more coatings of glue: But, on the 

 contrary, if the radiations of heat were facilitated and in- 

 creafed, it might be expelled that a greater effedt would be 

 produced by two coatings than by one. 



Exp, 3. The experiment was therefore tried, and it was Efp; 3* Mo« 

 found that the inftrument ufed employed only 37|- minutes in [ncrea£i*the "* 

 pafling through the interval. effeft. 



Exp. 4, 5, 6, 7. When the experiment was repeated with Exp. 4, 5, 6, y, 

 clear colourlefs fpirit varnith, the fame efFe6t was produced, ^.^^ ^^"^ ^*^' 

 and it was augmented as far as by four coatings. But on pro- 

 ceeding as far as eight coatings, the limit of the greateft effedl 

 was found to have been paflfed, 



Exp» 8, 9, 10. Black paint (lamp black and fize) upon the Exp. 8, 9, 10. 

 varnini increafed the cooling effea a little. When the inQru- ""•^"'^ ^^^ ^*" 



. . . . paint, 



ment was cleaned and then painted, its rapidity of cooling was 



nearly the fame = 35 minutes. And with white paint the dif- —and white, 



ference was not contiderable, as the efFe6l was produced in 



36 minutes. As the paint was laid on in feveral fucceffive 



coalings, the Count remarks that little dependence is to be 



placed on thefe refulls as indicating a difference from colour. '^ 



Exp. II. The clean infirument being fmoked black over a Exp. ir, 

 wax candle, was found to have cooled through the interval in ^^^ °^ fmoke 

 36-5 minutes, while the ftandard employed 53|- minutes. The 

 lamp black, when wiped off and weighed, amounted to lefs 

 than -j-^ of a grain, though it had completely covered 50 fquare 

 inches. 



With a view to a more accurate determination of the velo- 

 city of cooling, it was neceflary to afcertain what heatefcaped 

 through the permanent clothing at the ends. This was done Determination of 

 by obferving the times of cooling with and without the cloth- ^J^^ efcape of 

 ing, and comparing the effe6ts with the refpe6live furfaces of ends of the in- 

 expofure. For the whole furface of the inftrument 85.195 ftruments. 

 fquare inches, is to the furface of its vertical fides; fo is the 

 whole quantity of heat paffed off = 10000 to the quantity that 

 paffed through the fame fides = 5885. And fince by obfer- 

 vation the naked inftrument required 45 1 minutes to cool 

 through the fame interval as was paffed through in 551 "^'* 

 nutes when the ends were covered, the author concludes that 

 45| : 55f : : 5885 : 7015= what would have paffed in the 

 later interval through the upright furface, and confequently 

 that the remainder of the heat zi 2985 parts rauft have pafftfd 

 through the covered parts of the inftrument. 



