308 Scientific Intelligence. 
the principle that the induced current in a secondary coil depends 
with a telephone. If the primary coils are exactly equal, and are 
traversed by the same electric current, one will hear no sound 
by the introduction of metals on one side or the other, the tele- 
hone announces the inequality and the secondary coil has to be 
i he num 
metals. The extreme sensitiveness of this balance is shown by 
It is of use as a coin detector—any 
Professor Hughes’ balance, and gives a number of curves produced 
by different alloys, and shows that the balance can detect smaller 
quantities of metals in the composition of alloys than the methods 
hitherto used. He suggests also “that the balance ma afford a 
simple means of detecting variations in the molecular structure 
of alloys and for detecting allotropy in metals with greater acct 
— than has hitherto been possible.”— Fil. Mag., July, 1879, 
p. 50. am 
’ 
IL Grotogy anp NaruraL History. 
of South America. On the same day a great eruption occ 
in the island of Tanna, one of the New Hebrides, followed by # 
‘second outbreak on February 4. Simultaneously yet another 
Ph, 4 
erupt 
: ry 
volcano Isluga in South America (lat. 19° 10’ S.), where several 
villages were destroyed by the lava streams and accompauy!™g 
