Chemistry and Physics. 459 
same battery. Even more, if the primary current is too feeble to 
ring them, the secondary battery can by its accumulated work 
cause them to sound for a short time, thus forming a sort of ¢lec- 
influence of the secondary couple and begins to revolve iv the 
same direction in which it was turned to charge the battery. This 
result, which is precisely the opposite of what we should at first 
expect, is simply explained as follows. When the Gramme machine 
is turned, it generates a current in a certain direction. If now a 
er 
Sepiey Taynor, M.A., late Fellow of Trinity College, Cambridge. 
London: Macmillan & Co. 1873, pp. xii, 219, 8vo.—As the au- 
thor states in his preface, this treatise, “ portions of which have 
In thus endeavoring to remove the difficulties which non-mathe- 
matical readers find in attempting to follow and comprehend the 
expositions of the complicated phenomena of sound and music, the 
simple vibratory motions, or from several such combined ; thence 
original. The most unscientific reader cannot fail to be attracted 
by so simple and clear a presentation of an interesting subject, 
while the skilled acoustician may derive from 1t many valuable 
i A WO 
hints and suggestions, 
