NATURE 
227 
THURSDAY, OCTOBER 23, 1913. 
LORD RAYLEIGH’S SCIENTIFIC PAPERS. 
Scientific Papers. By John William Strutt, 
Baron Rayleigh, O.M., F.R.S. Vol. v., 1902- 
(Cambridge University 
1910. Pp, xiii+624. 
Press, 1912.) Price 15s. net. 
HE fifth volume of Lord Rayleigh’s 
papers contains his researches from 1902 
to 1910; it is a volume of nearly. eighty papers 
on subjects of a very varied nature—no slight 
record for a man during the seventieth decade of 
his life. 
The four. earlier volumes of the work have 
already been noticed in Nature, and there is little 
more to be said with regard to the volume now 
under review. ; 
The thanks of all interested in the advance of 
physical science are due in the first place to the 
author for thus reissuing in collected form his 
work during his own lifetime, and in the second 
to the Cambridge University Press for publishing 
it in the present admirable form. The issue 
of the collected works of great mathematicians— 
Adams, Cayley, Maxwell, Stokes, Rayleigh, Tait, 
and Kelvin—which the Press has undertaken in 
recent years has been of the utmost value to 
students throughout the world; and of this series 
no volumes have been more eagerly looked for 
or met with a more welcome reception than those 
of Lord Rayleigh. The pages under review 
afford ample evidence of the author’s. special 
powers, clearness of vision, whether in regard 
to the mathematical theory of his subject or to 
the essential details of an experimental inquiry; a 
firm grasp of mathematics as an instrument to 
solve the problem he is attacking; readiness to 
use simple methods of experiment where these 
suffice; the power to see when it is necessary 
to call in the highest skill of the instrument- 
maker or the minute care of the observer—these 
are manifest throughout. 
It must suffice for the present to refer to one 
or two of the papers which appear of most interest 
to the present writer; the volume must find a 
place on the shelves of every physical library, and 
be continually referred to by students and workers. 
One of the earliest papers reprinted from the 
Phil. Trans. for 1902 deals with the isothermal 
relation between the pressure and volume of a 
gas at pressures of from 75 to 150 mm. of mercury. 
The conclusion reached is that to one part in 
5000 at least air, hydrogen, oxygen, and argon 
obey Boyle’s law at the pressures concerned and 
at ordinary temperatures (10°—15°). For nitrous 
oxide the deviations are somewhat greater. The 
NO. 2295, VOL. 92] 
work was extended to higher pressures up to 
one atmosphere in a further paper (Phil. Trans., 
1905). 
In two interesting papers the question whether 
the earth’s motion affects the rotatory polarisation 
or produces double refraction of light are both 
answered in the negative. Other papers, again, 
bear evidence as to Lord Rayleigh’s activity 
as a member of the’ Explosives Committee, or 
as adviser to the’ Trinity House, while 2 
large part of the’ volume deals with various 
problems of small vibrations either optical, acous- 
tical, or electrical, e.g. on the bending of waves 
round a spherical | obstacle ; on. the dynamical 
theory of gratings; on the application of Poisson’s 
formula to discontinuous disturbances, together 
with a series of acoustical notes. 
Reference should also be made to a series of 
papers dealing with the measurement of the wave- 
length of light, commencing with one in the Philo- 
sophical Magazine for 1906, on some measure- 
ments of wave-lengths with a modified apparatus, 
followed by another on further measurements of 
wave-lengths, Phil. Mag., xv., 1908. Both these 
papers are admirable examples of Lord Rayleigh’s 
method of dealing with experimental difficulties 
of a high order without any undue elaboration of 
apparatus, and of his success in securing results. 
The method employed was a modification of that 
of Fabry and Perot, and the observations re- 
corded in the first paper verified to one part in 
a million the values found for the wave-lengths, 
in terms of that of the red cadmium line, of the 
more important lines of cadmium, mercury, zinc, 
and soda, by Michelson and Fabry:and Perot. 
In conclusion reference should be made to 
papers on skin friction on even surfaces, a note 
to a paper by’Prof Zahm, Phil. Mag., 1904, and 
on the application of the principle of dynamical 
similarity, Reports of the Advisory Committee for 
Aéronautics, 1909-10 and I9gI10-Tt. 
These deal with the conditions to be observed 
when calculating the resistance on bodies moving 
through the air from experiments on models. 
On the assumption that the resistance depends on 
the velocity and viscosity of the air and on the 
size of the surface, and is approximately propor- 
tional to the square of the velocity, it is shown 
that the resistance R is given by the equation— 
R=pV%¥(v/V)), 
where p, V, and v= are the 
velocity, and viscosity of the fluid, and 1 a linear 
density, 
| quantity defining the size of the body, f being 
an unknown function. It follows from this that 
if the resistances are to be treated as proportional 
to the squares of the velocities for the actual 
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