266 



On the Heat-conductivity of Stone. 



Table {continued). 



Time, in 

 minutes. 



Observed 

 tempera- 

 ture of 

 compen- 

 sating 

 bath. 



22 



m 



23 



23* 

 24 



24* 



25 



25* 



26 



26* 



27 



27| 



28 



29 



291 



30 



30* 



31* 



32 



35 



36 



37 



38 



39 



41 



42 



43 



44J 



46 



48 



Galvano- 

 meter- 

 reading. 



38-5 C. 



38 



36-8 



36 3 



35 6 



34 2 



341 



33 



32-9 



32-5 



32 



314 



311 



30-8 



29-2 



292 



286 



28-5 



278 



271 



26-8 



26- 1 



247 



24-3 



237 



23 



23 



221 



217 



214 



209 



20 3 



20 



176 



17E 

 23 E 



6E 

 10E 



5E 

 27 L 



8L 

 28L 



10 L 

 6L 

 4L 



15L 

 5L 

 8E 



29 L 

 9L 



15L 

 1L 

 2L 



11 L 

 5E 

 6E 



15 L 

 11L 

 14L 

 25 L 

 6L 

 16L 

 22 L 

 12L 

 13 L 

 11L 

 75 E 

 11 L 



Galvano- 

 meter 

 zero. 



Tempe- 

 rature of 

 stream of 



water. 



Value of 

 galvanome- 

 ter deflec- 

 tion in de- 

 grees Cen- 

 tigrade. 



185 

 18"" 

 f8 : " 



79 



17 : 8 



17 8 



17 : 8 

 177 

 17-T 



if" 



True tem- 

 perature of 

 centre of 

 ball. 



-0 4 

 -0-5 

 -01 

 -02 

 -01 

 +0-6 

 +02 

 + 0-6 

 +02 

 +0-1 

 +0-1 

 +0-3 

 +01 

 -0-2 

 + 0-6 

 +0-2 

 +0-3 









 +0-2 

 -01 

 -01 

 +0-3 

 +0-2 

 + 0-3 

 +0-5 

 +0-1 

 +0-3 

 +0-5 

 +0-3 

 +0-3 

 +0-2 

 -1-6 

 +02 



381 i 



375 



367 



361 



35-5 



34-8 



34-3 



33 6 



331 



32-6 



321 



317 



31 2 



306 



29-8 



29-4 



28-9 



285 



27-8 



273 



267 



26 



25 



24-5 



24 



23-5 



23 1 



22-4 



22-2 



217 



21-2 



20-5 



18-4 



17-8 



To illustrate the mathematical results in connexion with the 

 cooling of a globe, given by Fourier in his treatise De la 

 Chaleur, we have drawn figures 6 and 7. A ball of 6*9 cen- 

 tims. radius, having an internal conductivity 0*00590 (centim., 

 second) and an emissivity 0*00252, is supposed to have been 

 heated all to a uniform temperature and then kept in a stream 

 of cold water at constant temperature. The exisothermal curves 

 PAAA, PBBB, PCCC, PDDD, PEEE, PFFF 

 (PL X. fig. 6) represent respectively the time-fall of tempera- 

 ture of points situated — 



