Notices of Books. 
273 
the entire work. Commencing with an account of the compass 
and dipping-needle, the subjedt of lightning-condudfors is next 
discussed, and this is followed by the great subject of eledtric 
telegraphy. This receives very ample discussion, and all the 
newest improvements are described. The eledtric light is now 
employed far more generally than it used to be, and apparently 
it is far from expensive. The eledtric light which was employed 
in the clock tower of the Houses of Parliament was produced 
by a Gramme machine driven by a two horse-power eVigine at a 
rate of 320 revolutions per minute. It is stated that it produced 
“ a light equal to 7000 sperm candles, at a cost of about one 
shilling per hour.” The eledtric light, which is employed for 
many stage effedts, at the Grand Opera in Paris is produced by 
360 Bunsen elements. The application of this intense light 
to the lighting of towns has not proved a success : it is probable, 
however, that if a great elevation could be secured, it might be 
used with advantage. It would be interesting to try the effedt 
of the light on the top of Strasburg Cathedral. A few general 
applications on eledtricity conclude the fifth book and the 
volume. 
This new work of M. Guillemin is a useful adjundt to his 
former volume on the physical forces ; it does not, however, 
present the same features of novelty to the general reader, 
because the former volume, on account of its popular nature, 
could not well avoid allusions to some of the pradtical applica- 
tions of the forces which it described. 
Acoustics, Light , and Heat. By William Lees, M.A. London 
and Glasgow : William Collins and Co. 1877. 
Messrs. Collins are doing good service to the cause of scien- 
tific education by issuing a cheap and generally excellent series 
of text-books. There are two series of such books — an 
“ Elementary ” or Primer Series, and an “ Advanced,” usually 
by the same author. The elementary volume of the present 
work has been published for some length of time, and has been 
found a fairly useful book for science classes in schools. The 
work before us embraces all that can be required by the advanced 
classes in schools ; it is well illustrated, and in the main clearly 
written. 
VOL. VII. (N.S.) 
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