444 DR. CHAKLKS It. LKfcS ON THK KFFKCT OF TKMPKKATUUK OX TllK 



the surface of a cylinder of radius r, with its axis parallel to the x axis, is equal to 



I,, ( -? ) times the mean value of u along the axis of the cylinder. 



If the circle of radius p has its centre q from the singularity J '(x) . K u (?)> : 



\ 21 / 



encloses that singularity, we have, since 



p = \/q*+p a +2qp cos and p > q, 



Hence the mean value of K 



along the circle 



and the mean value over the surface of a circular cylinder of radius p with its axis 

 parallel to the source and distance q from it = I - ^"" times the mean 



times the value 



value of f (x) along the length of the source within the cylinder. 



The two spirals of thin platinum wire, whose resistances give their mean tempera- 

 tures, had the same radius p, were of the same length, 2s, and were situated at the 

 same distance from l e axis of the cylinder. One had its axis coincident with the 



source. The temperature f , indicated by it was therefore = K ( f- ) times the mean 



\ 2,1 I 



value of f (x) along the length 2.s of the source within it, + 1 



of ' due to the remainder of the expression for t> above. 

 I.e., 



f,-V=-^L- j ! {1 -(_!)} sm !!?.!(' cos ^.(Zz 

 2irkir,~ l n l 3 0J 21 



K l' nva \ 

 



K, 



\ 21 



