REVIEWS. 
429 
not space for an analysis of the contents, but we may offer a few of tbe head- 
ings of tbe chapters, as indicative of tbe wide range of subj ects discussed : — 
Nature of sound, its propagation ; Newton’s and Laplace’s formulae ; influence 
of beat, density, and elasticity ; vibration of sound in various bodies ; distinc- 
tion between music and noise ; periodic and unperiodic impulses ; vibration 
of tuning-fork 5 tbe syren ; wave-lengtbs of tbe human voice ; vibration of 
strings j sound-boards j nodes and ventral segments j timbre ; overtones j 
clang-tint ; special harmonics and their abolition ; vibrations of rods ; 
kaleidopbone ; musical box ; harmonica ; disks and bells ; longitudinal 
vibration of wires ; vibration of pipes, stopped and open ; resonance reeds ; tbe 
organs of voice ; sounding and sensitive flames, &c. ; vibratory motions in 
water and air ; destruction of sound by sound ; theory of beats ; optical 
illustration ; resultant tones ; combination of musical sounds ; theories of 
consonance and dissonance ; interference of primary tones and overtones ; 
musical chords ; mechanism of hearing, etc. Those above all who are in- 
terested in music, and desire to appreciate the cause of the singular effects 
so well known to musicians, should read Dr. Tyndall’s volume, in which 
they will find a veritable mine of wonderful facts. The description of the 
Syren alone is a dissertation on the theory of music. For clearness of 
diction, and simplicity of explanation, this book stands unmatched. It is 
the best popular treatise on sound ever published, and it is withal the most 
comprehensive and accurate student’s handbook on the science of acoustics. 
ASTRONOMICAL HETERODOXY.* 
O UR readers, of course, accept the ordinary doctrine of astronomers, that 
the earth moves round the sun : indeed, we are disposed to think that 
many would resent any attempt to turn their faith on this point as a piece 
of insanity. There are few of us so calm as the metaphysician who 
alleged that if a man bearing a reputation for common sense came to him and 
said that two and two make five, and not four, he would listen to him and hear 
his arguments. But, after all, the acceptance of a faith, no matter how general 
or implicit it be, is no criterion of its soundness. It must be remembered 
that when it was first asserted that the earth moves round the sun, and not the 
sun round the earth, the assertion was not only listened to with doubt, but 
was rejected with derision. Besides, it must be confessed that the demon- 
stration of the absolute movement of the earth round the sun is by no means 
the easiest matter in astronomy. To prove a relative movement is no dif- 
ficult task ; but to decide which of the two, the sun or the earth, is the 
fixed and which the moving body, is a problem which is certainly none of 
the simplest. The author of the brochure before us, tries to show not 
only that this is difficult; but that it is impossible. He does not deny 
for a moment the fact of a relative movement of the sun and earth ; but he 
contends that there is no mathematical evidence to prove that it is the earth, 
and not the sun, which performs the orbital circuit. The arguments he 
adduces to show the fallacy of our present proofs are both numerous and 
* 11 The Theories of Ptolemy and Copernicus.” By A Wrangler. London: 
Longmans. 1867. 
