ON HEA,T\ 



61 



called the Paflage Thermometer*, may be ufed to make a 

 number of interefting experiments on the cooling of bodies 

 through different fluids. In the prefent experiment I em- 

 ployed it in the following manner: 



The interior veflel was entirely filled with hot water to the J he inner vef- 

 ... rii/* .... , . ,, A id was filled 



height of half an inch in its neck, and a good thermometer, with hot water, 



having its cylindric bulb four inches long, was inferted therein, and a thermo- 



The inftrument was then plunged in a mixture of pounded ice ^neck! 06 



and water, and the time was noted by means of the thermo- The whole in- 



meter, during which the hot water in the fmall. veflel became f^pTun^d in 



cold. •• '• ice andjwater. 



I was careful to plunge the inftrument in this frigorific 

 mixture, fo that the large veflel was completely fubmerged 

 except the upper extremity of its neck ; and I added from 

 time to time a fufficient quantity of pounded ice, to keep the |» 

 frigorific mixture conftantly and throughout at the temperature 

 of melting ice. 



The following were the refults afforded by two fimilar in- # « § 

 ftruments employed at the fame time : 



Thefe two inftruments, which I fliall diflinguifh refpectively Rc /v ks w ' th 



by the letters A and B, are of the fame form and dirnenfions j one f ^hich 



there is no difference between them but in the (rate of their B, had the itite- 



furfaces. In the inftrument A, the exterior furface of the ^ ^ItLl 



fmall veflel and the interior furface of the great veHfel which and the exterior 



inclofes it, are bright and polifhed ; but in the inftrument B, J^*/™"" 



the exterior furface of the fmall veflel and the interior furface the other inftru- 



of the large veflel are black, having been blackened over the ,nent » A > h * d 

 n c ii i <• i i r i - , the like furfaces 



flame ot a candle before the bottom of the great veflel was po iimed. 



foldered in its place. 



Having filled the interior veffel of each of thefe inftrument* The interior 

 with boiling water till the water rote to the height of half an toU^g watet^ 

 inch in the neck, I placed a thermometer in each, and then 

 plunging both infiruments at the fame time into a tub filled 

 with cold water mixed with pounded ice, I obferved the 

 courfe of their refrigeration during feveral hours. 



Each of the inftruments was completely fubmerged in the The refrige-at- 

 frigorific mixture, excepting about one inch of the fuperior in . 8 v ^ el con * 



. . . \ F , ° . _ r tamed lee and 



extremity ot tbe neck of the exterior veflel, and I was careful water. 



* See our Journal Vol. IX. 



F2 to 



