118 Pte. J. A. Hughes on the 



On using the formula o£ Gauss 



we get, without much difficulty, 



wT n = 2n[log{\ncot(i\ir)}-^(l-\n)~if(l+\72)] 



t \mT> 



' m ti (2m) ! (2^) 2 — i )Y [2 2 J tr [2 + 2 K > 



_^—l)(l_l X ) _^(2— D(l + lX)f , 



the remainder after r terms having the same sign and being 

 numerically less than the (r + l)th term; where \ is equal 

 to /3/(2tt). 



The corresponding series occurring in the transverse 

 component of force is 



U w == z, cos -/3)eosec 2 ( — ^/3 ) 



m =i \ n 2 / \n 2^ / 



o oT» 1 ~d r Ln 



this may be determined from the asymptotic expansion for 

 T n , which may legitimately be differentiated term by term 

 with respect to X. 



XVII. On the Cooling of Cylinders in a Stream of Air. By 

 Pte. J. Alfred Hughes, B.Sc, E Coy, R.A.M.C, for- 

 merly Research Student, University College ofJSo?'th Wales, 

 Bangor*. 



THE interchange of heat between a solid and a moving 

 stream of gas is a subject oflconsiderable technical import- 

 ance, and also not devoid of scientific interest. A considerable 

 amount of work has been done on the cooling of thin wiresf 

 in a current of air, mainly with the object of constructing 

 instruments for the measurements of air-velocity. These 

 experiments have shown that the heat lost by the wire is 

 proportional to the difference of temperature and to the 

 square-root of the velocity. There are, however, no data 

 available relating to the convection of heat from bodies of 

 large diameters; and the following experiments were under- 

 taken with a view of throwing some light on the problem of 

 convection in these cases. 



* Communicated by Prof. E. Taylor Jones, D.Sc. 



t King, Phil. Trans. 1914, p. 873. Morris, ' Electrician,' Oct. 4, 1912. 



