1875.| Notices of Books. 527 
An appendix of more than 200 pages will be found at the end 
of the work. Much of this has been added by the translator. 
Among other matters of interest which it contains, we may 
notice an account of an electro-magnetic driving machine for 
the siren. This machine gives perfect uniformity of rotation, 
and perfectly constant tones can be produced by the means. Air 
is driven through the siren by means of a small turbine of stiff 
paper. In discussing the size and construction of resonators, 
the author mentions that he first employed spherical glass vessels 
for the purpose, but now more generally vessels of brass. He 
also used tubes of tin and pasteboard. A table shows the exact 
size and capacity of resonators, adapted to tones of different 
pitch. A number of mathematical papers follow, and a very 
good index terminates the volume. 
It is almost unnecessary for us to say that this already famous 
book will be welcomed alike by the physicist, the acoustician, 
and the musician. It is one of the most original works of the 
second half of this century, and may be placed in the same 
category as the ‘ Natural Philosophy” of Thomson and Tait, 
and the ‘‘ Electricity” of Clerk Maxwell. 
Sound. Third Edition. By Joun TynDAtt, F.R.S. London: 
Longmans and Co. 1875. 
Six Lectures on Light. Delivered in America in 1872-73. By 
Joun TynpDALL, F.R.S. Second Edition. London: Long- 
mans and Co. 1875. 
WE are very glad to welcome new editions of these standard 
works. One of the great merits of Dr. Tyndall as an expounder 
of scientific facts is that he is not alone content to read the 
memoirs of authors whom he is desirous of quoting, but that he 
himself goes through their experiments, and seldom gives an 
account of an experiment which he has not himself tried. His 
works thus become of especial value to the lecturer and science 
teacher. ‘The main feature in the new edition of the ‘‘ Sound” is 
the introduction (in chapter 7) of the author’s recent experiments 
on ‘* The Acoustic Transparency of the Atmosphere in relation 
to the Question of Fog-signalling.” This subject has been so 
recently discussed in nearly all the scientific journals, that it will 
be familiar to all of us. The preface gives an account, in some 
detail, of the controversy between Dr. Tyndall and the United 
States Lighthouse Board, as to the priority of claims. A review 
of Dr. Tyndall's ‘“‘ Lectures on Light” appeared not long ago in 
this journal, and we have but little to add in noticing a second 
English edition; the only very noticeable alteration in this edi- 
tion is the omission of the author’s “ Reply to the Edinburgh 
Reviewers,” concerning the claims of Dr. Young, and the inser- 
tion of a portrait of Dr. Young at the commencement of the 
VOL. V. (N.S.) 2% 
