and 



String Galvanometer of Einthoven. 221 



the second term is then confined to the first part of the curve 

 affecting the shape of the first descent to zero. AVith very 

 fine fibres, 0*001 mm., the tension cannot be safely increased 

 to such a value as to make the string oscillate in air at the 

 ordinary pressure. 



Case of return to zero position in a uniform 

 field ivlien n s < -£ . 



When the tension is such that ??J = —r-\ /_i)is less than 



Jfe, the form of solution is given by (31.) from which we 

 find 



lA x e +B^ jsm-^-+( A 2 <? +B 2 e Isin— v- + .... (55) 



y 



^A^'e i-B^'e J sin — + y A^e ' + B 2f i 2 "e ' jsin-y-+. (56) 



Putting £ = in (55) and equating coefficients to those for 

 the approximate circle in (9), we find, when s is odd 



1 32 



A *+ B -=;^ryo (57) 



When even 



A, + B, = 0. 



Equating all the coefficients in (56) to zero and combining 

 with (57) we have, when s is odd, 



A 1 32 M> " 



A9 =~? + W=ff > * (58 > 



i t~» 1 32 aJ 



and Bs = ?v>w5z i *° (59) 



When s is even A s =B, = 0, and hence 



32 r i / h 't k'k . wx 



+ 3W=/? 7 )l~^ 3 +/ * 3 " J sln ~ + ••••r • (b0) 



