436 
NATURE 
[Maxkcu 7, 1907 
the vision and hearing of every child under their 
care. It is manifest that ‘“‘the more the teacher 
knows about the health of the children entrusted to 
him, the simpler and easier will the work of medical 
inspection become’’ (p. 61). We therefore suggest 
cooperation between the teacher and doctor in the 
manner indicated. 
The above quotations and remarks will amply serve 
to show the general interest of Dr. Mackenzie's little 
volume. It is true that three of the four chapters, 
entitled ‘‘The Hygiene of School Life,’” “* Normal 
Growth in the School Ages,’’ ‘‘ Medical Examination 
and Supervision of Schools and School Children,” 
contain much that has been written of, if perhaps 
less attractively, before. But the remaining chapter, 
“©The School Doctor in Germany,’ and the appen- 
dices on “‘ Re-vaccination of School Children in Ger- 
many ’’ and on “The Plan of a German Elementary 
School,’’? traverse comparatively unfamiliar ground, 
and well deserve the attention of the serious student. 
Cy SyaMe 
ELEMENTARY PHYSICS. 
(1) Exercises in Physics for the Use of Schools. By 
J. H. Leonard and W. H. Salmon. Pp. vii+116. 
(London: J. Murray, 1906.) Price ts. 
{2) Introductory Practical Physics. By W. F. Barrett 
and W. Brown. New edition. Part i. Pp. xii+ 
284. (London: Simpkin, Marshall and Co., Ltd. ; 
Dublin: Sealy, Bryers and Wallser.) 
(3) Heat, Light, and Sound: an Introductory Course 
of Practical Exercises. By J. R. Ashworth. Pp. 
xv+i20. (London: Whittaker and Co., 1906.) 
Price 2s net. 
(4) Light for Intermediate Students. By ¥. E. Rees. 
Pp. viii+166. (London: J. M. Dent and Co., 1go6.) 
{s) The Tutorial Physics. Vol. iii. A Text-book of 
Light. By Dr. R. Wallace Stewart. Fourth 
edition. Revised by J. Satterley. Pp. viii+ 346. 
(Cambridge: University Tutorial Press, Ltd., 1906.) 
Price 4s. 6d. 
(6) The Elements of Physics. By S. E. Coleman. 
Pp. vii+439. (Boston: D. C. Heath and Co., 1906.) 
Price 3s. 6d. 
(7) Physics—Theoretical and Descriptive. By H. C. 
Cheston, J. S. Gibson, and C. E. Timmerman. 
Pp. xvi+373. (Boston: D. C. Heath and Co., 
1906.) Price 3s. 6d. 
(8) A First-year Course of Practical Magnetism and 
Electricity. By Dr. P. E. Shaw. Pp. vii+66. 
(London: Electrician Printing and Publishing Co., 
Ltd., n.d.) Price 2s. 6d. net. 
(1) aN GRADUATED collection of simple arith- 
metical exercises in physics, including 
mensuration, mechanics and hydrostatics, which will 
prove useful for school classes. No examples are 
given on heat conductivity. Answers are furnished. 
(2) This text-book will be found useful for both 
elementary and advanced students. The volume deals 
with general physics, and the experiments described 
cover a wide range. They include measurements of 
length, area, volume, time, and mass; experiments on 
fluid pressure; measurement of force; mechanical 
NG. 1949, VOL. 75 | 
properties of solids and liquids; molecular properties 
of fluids. The method of carrying out each experi- 
ment is briefly described, and an example is worked 
out in illustration. Theoretical considerations are 
generally avoided, but many references are given to 
text-books or original sources, so that a student may 
obtain further information if he desires. With such 
a wide range of subjects in so small a book, the 
treatment is often scant in places, e.g. the plani- 
meter is dismissed without any mention of the datum 
circle. On p. 147 it is not at all clear how the mean 
value of Poisson’s ratio is obtained from the recorded 
data. In the experimental proof of Boyle’s law, one 
is told first to adjust the mercury to the same level 
in each limb of the tube; this very tedious operation 
is hardly necessary. There is little meaning in the 
statement on p. 123 that the value of g determined 
by simple pendulum experiments is 0.12 per cent. 
greater than the true value. 
(3) Dr. Ashworth’s book comprises a course of 
laboratory experiments in heat, light, and sound for 
first-year students. The plan adopted with each 
exercise is to give a list of the apparatus necessary, 
a short description of the method of carrying out 
the experiment, and a typical example to show how 
results are to be recorded in the note-book. It is to 
be regretted that these examples are not always well 
chosen. In the experiments on calorimetry, the 
temperature changes produced are often too small 
for measurement with any dégree of accuracy by 
elementary students. There is little to be gained by 
comparing 78-9, the determined value of the latent 
heat of water, with an accepted value of 79-3 when the 
temperature change in the calorimeter is 5°.5 C. The 
example on the determination of the refractive index 
of glass, by tracing the ray through a slab, is bad. 
Measured lengths of perpendiculars from the incident 
and refracted rays on the normal vary from 0.5 cm. 
to 1-0 cm., and the mean value of the refractive index 
is stated as A further illustration is afforded 
in an experiment to investigate the relation between 
the time of vibration of a spring of constant length 
with varying load. Recorded periods are 0.54 and 
0-64 second; their ratio 1.185. The ratio of the square 
roots of the corresponding masses is given as 1-183, 
and the error is stated as 0-2 per cent. 
(4) This little book is intended by the author for 
students with some previous knowledge of experi- 
mental optics. The subject-matter covered, however, 
is very elementary, and the treatment is rather formal 
and meagre. Two chapters, devoted to intrinsic 
brightness and photometry, are very clear, and will 
serve as a useful introduction to more advanced works 
on photometry. Two excellent photographs of models 
taken with a pin-hole camera are furnished by Mr. 
Andrew Stephenson, and a graphical proof of the 
minimum deviation position is due to him. Lens 
and mirror formula are derived in the ordinary way. 
The curvature method for obtaining these formulz is 
not introduced, and no mention is made of the term 
““power of a lens.’’ The book is attractive in appear- 
ance, and many students will probably find it useful 
for revision purposes. 
I-52. 
