92 Mr. D. M'Farlane on the Surface-conductivity [Jan. 11, 



The numbers found in cols. VI. and VII. were plotted on squared paper, 

 a nd a mean curve drawn through the points ; and, assuming the quantity of 

 heat emitted to be represented by the formula x=a + bt-\-ct 2 , where t is 

 the difference of temperature, the coordinates of the curve were employed 

 to determine a, b, and c; and col. VIII., calculated by the formula, is 

 added to show the degree of approximation to which the results of the 

 experiment are represented by it. 



First Series. 



Atmosphere moist. Copper Ball polished bright. 

 Means of nine sets of Observations. 



I. 



II. 



m. 



IV. 



V. 



VI. 



VII. 



VIII- 



Mean 



Difference 









Heat emitted 

 per second 



Mean difference 



Heat emitted 



deflections 

 of nine sets 

 of observa- 



of 



tempera- 

 ture, 



logic D- 



logic D'-logToD'' 



log € D'-log e D" 



of tempera- 

 ture, 

 i[D'-D"J, 



per second, 

 calculated by 

 formula, 



4 



4 



by observa- 

 tion. 



tions. 



D. 







c. 



CO. 



(*). 



627-19 

 576-28 

 528-82 

 484-50 

 444-14 

 407-15 

 373-37 

 342-26 

 313-64 

 287-89 

 264-42 

 243-58 

 223-96 

 206-15 

 190-20 

 175-57 

 161-99 

 149-51 



66-88 

 60-79 

 55-21 

 50-10 

 45-51 

 41-38 

 37-64 

 34-28 

 31-21 

 28-48 

 26-02 

 23-85 

 21-83 

 20-01 

 18-39 

 16-92 

 15-56 

 14-32 



•82527 

 •78380 

 •74200 

 •69981 

 •65815 

 •61681 

 •57570 

 •53509 

 •49429 

 •45459 

 •41529 

 •37756 

 •33907 

 •30127 

 •26467 

 ■22845 

 •19207 

 •15603 



•01037 



•02387 



•000223 



63-83 



•000230 



•01045 

 •01055 

 •01041 

 •01033 

 •01028 



•02406 

 •02429 

 •02396 

 •02378 

 •02366 



•000226 

 •000227 

 •000225 

 •000223 

 •000222 



5800 

 52-65 

 47-81 

 43-45 

 39-51 



•000227 

 •000226 

 •000224 

 •000222 

 •000220 



•01015 

 •01020 

 •00992 



•02337 

 •02348 

 •02284 



•000219 

 •000220 

 000214 



35-96 

 32-75 

 29-85 



•000217 

 •000215 

 •000213 



•00982 



•02261 



•000212 



27-25 



•000210 



•00943 

 •00962 



•02171 

 •02215 



•000204 

 •000208 



24-94 

 22-84 



•000208 

 •000205 



•00945 

 •00915 



•02175 

 •02106 



•000204 

 •000198 



20-92 

 19-20 



•000202 

 •000200 



•00905 

 •00909 



•02083 

 •02093 



•000195 

 •000196 



17-62 

 16-24 



•000198 

 •000196 



•00901 



•02074 



•000195 



14-94 



•000194 



Formula for calculating column VIII. : — 



cc= -000168 + •00000198*--0000000m 2 . 



gramme-water units. let cc denote the beat emitted per second, per sq. centimetre 

 per degree of difference of temperature, and C the rate at which the difference of tem- 

 perature varies per minute ; then 



ccx 60 X 50-26 _ c 

 28-31 



and therefore 



-009385 C. 



