FOE DETEEMINING THE EADIATINQ- POWEES OF SUEFACES IN AIE. 397 
III. Same Disc of Glass. 
Time =300 beats. 
Height of barometer =30'3 inches. 
= *76 metre. 
Number of 
experiment. 
Temperature of the 
radiating surface. 
Headings of the 
calorimeter. 
Difference of the 
readings =E.2 — Ej. 
Temperature 
of the air. 
(1) 
rTi = 378-5l 
\T2=378-5/ 
/Ri = 66-81 1 
IR 2 — 66-25/ 
5-44 
0 
62 
(2) 
f Ti=380-0Y 
\T2= 380*5/ 
/ Ri=6l-02\ 
1 R2=66-20 / 
5-18 
(3) 
f Tj=381-5l 
1.T2=380-0 / 
/Ri = 58-53\ 
1R2=63-74/ 
5-21 
61 
(4) 
JT, =380-0 1 
tT2=381*3/ 
J Rj = 58-90'l 
1R2= 64-10/ 
5-20 
(5) 
f Ti = 384-0l 
1X2=382-5/ 
/Ri = 59-13l 
1R2=64-55/ 
5-42 
62 
(6) 
Ti=378-0 
/Ri=59-361 
1R2=64-74/ 
5-38 
(7) 
/Ti= 375-51 
1X2=376-0/ 
rRj=59-63\ 
1R2=65-10/ 
5-47 
Taking the means, we obtain 
(T)=379°-70 (F.) 
(R)= 62°-29, 
(T)-(R)=317°-41; 
and hence from the mean of these seven experiments we have 
0= 16°-6 (C.), 
if=175°-4, 
Rj — Ili= 5*33 for 300 beats, 
and therefore 
Rg — R,= 8'88 for 500 beats. 
13. Recurring to equation (2.), art. 3, and substituting the numerical values for A, 
and B„ adopted by Dulong and Petit, we have 
Q=m{2-037aV'-l)+'00919/«^‘''®*}; 
or putting the last term in a form which may in some' cases be rather more convenient 
for numerical calculation, we shall have 
Q=m{2-037a«(a^-l)+-00793(^:|2y'V'^^^} (6.) 
Our first object is the determination of m, and for this purpose we must substitute 
