448 
:\JR. GE0RC4E W. WALKER ON THE DEPENDENCE OF THE 
We may take the ratio for the original hydrogen as 
3-141 ± -003 
1 + t (-00350 d: -00003) ’ 
wliich gives for the refractive index 
= 14- '0 001 407 ± -00000015 £ 
^ [ I -\-t (-00350 d: -00003)} 76 ' 
Ammonia. 
1 he gas was prepai'ed dry liy the following method, for which I am indebted to 
Dr. Scott, of the Davy-Faraday Laboratory. 
A strong solution of ammonia, in a glass flask, was gently warmed, and the gas 
passed first tiirongh a tube containing dry caustic potash and next through a tube 
