NATURE 
[APRIL 22, 1897 
magnetised toroid is adopted, and then the following state- 
ment ismade. ‘Then in accordance with § 99 there 
will be 47I lines of force passing across each square 
centimetre of the gap, and these continue their course to 
the same number through the substance of the toroid.” 
The latter part of this statement is wrong if we allow 
that the force at every point of the field can be calculated 
from the law of inverse square, for the surface distribution 
of magnetism on the opposite faces of the gap is + and 
—1; so that if the gap is narrow the force in the gap is 
471, but is zero at every other part of the field, including 
the substance of the toroid itself. Apart from this, the 
book itself contains a statement which directly con- 
tradicts the idea of there being any force inside a 
uniformly magnetised toroid, for on page 120 the follow- 
ing sentence occurs. “Since such a toroid neither emits 
nor absorbs lines of force, it is without magnetic in- 
fluence. In its interior also it may be shown that its 
magnetic force vanishes.” 
The second section contains a full account of the 
elementary properties of the electro-magnetic field of 
force. The diagrams showing the directions of the lines 
of force in the various cases are especially instructive, 
and are arranged in a manner that would assist the 
student to form a mental picture of the position of the 
lines of force for simple conductors. 
Questions involving mathematics are avoided through- 
out the whole book, so that it would be ill-suited for a 
student who could arrive at all the results by the appli- 
cation of simple mathematics. There is, unfortunately, 
a large number of students who learn physics without 
having a mathematical training, and they will no doubt 
find in Part i. much useful information, and experimental 
proofs of the various properties of magnetic forces due 
to magnets or electric currents. 
A list of errata would have been useful, as there are 
a few misprints, as on pages 81 and 86, in the dimensions 
of the units. 
Part i. only contains the elementary theories ; but in 
Part ii. the author intends to treat of the more advanced 
branches of the subject which come under the head of 
induction and electrical oscillations. Jenoeeile 
A Study of the Sky. By Herbert A. Howe. Pp. xii + 335. 
(London: Macmillan and Co., Ltd., 1897.) 
IN these pages the author presents his readers with a 
popular and general account of the more prominent 
features of the heavens, and describes how astronomers 
have been able to gather such information. After ashort 
historical sketch of the founders of astronomy up to 
the end of the eighteenth century, a series of chapters is 
devoted to the various constellations, showing how each 
particular one may be recognised, and at what time of 
year it is best visible: the diagrams accompanying 
these will be found very distinct, and undoubtedly useful. 
The author then devotes a chapter to the character of the 
astronomer, acting on the idea that the personality of the 
observer is a powerful factor in his scientific utterances. 
The illustrations accompanying this chapter are restricted 
to American astronomers, and will be of special interest 
to those who know the works, but have not made the ac- 
quaintance, of celestial investigators, across the Atlantic. 
Reference is next made to the astronomer’s implements 
and observatories : in this the-great refractors of America, 
and a description of the preparation of the lenses, are 
dealt with, followed by a very sparse account of spectrum 
analysis. A few pages are devoted to the measurement of 
time, and the general features of the solar surface are next 
venerally described. Some excellent lunar reproductions 
are inserted in the text relating to the moon and eclipses, 
and the planets come in for a good share of description, 
reference being made to most of the recent work done in 
this branch of observational astronomy. The progress 
made in celestial photography is well illustrated in those 
sections dealing with comets, nebulz and stars ; but the 
NO. 1434, VOL. 55] 
information is at times somewhat scanty—as, for instance, 
the dismissal of stellar spectra in about one hundred lines. 
As a whole, the book is well worth perusal, and its value 
is considerably enhanced by the wealth of excellent 
illustrations throughout. The general reader, as well as. 
the student, will find in it much that is interesting. 
The Clue to the Ages. Part I. 
By Ernest Judson Page. Pp. xii + 282. 
Baptist Tract and Book Society.) 
THERE are species, varieties, and sub-varieties of human 
societies and human character, just as there are of 
structural organisms. Says the author: “The recorded 
histories of the centuries are as geological strata in 
which are imbedded the records of the origin of species. 
of character, by which to test, and, if necessary, correct 
Darwin’s theory. Regarding differing ecclesiastical and 
national types as true species and varieties of character, 
the question arises—Does the Evolutionary Hypothesis 
sufficiently account for the Origin of Species? My 
answer is most emphatically that species of human 
character have not arisen, and do not arise, according to 
Darwin’s theory.” Having proved to his satisfaction 
that evolution is insufficient to explain social develop- 
ment, the author propounds an alternative theory which 
he submits to the kind consideration of an indulgent 
public. 
Who's Who, 1897. Edited by Mr. Douglas Sladen. 
vill + 823. (London: Black, 1897.) 
THIS is certainly a most useful book to have on a library 
table ; for it is a hand-book of not only those who inherit 
distinction, but also of those who are officially prominent, 
and others whose ability has brought them before the 
public. Information may also be obtained regarding 
the Royal Family, Army, Navy, the Government, Uni- 
versities, Church, &c.—in fact, all societies: and institu- 
tions with which we are brought into daily contact. 
There is also a complete list of the Fellows of the Royal 
Society, and a useful table of pseudonyms. We notice 
that the short biographies, which form the greater part 
of the book, include a large number of scientific men. 
The book is very neatly got up, is bound in a good 
flexible cover, and is excellently printed. 
Creation by Principle. 
(London : 
Pp. 
LETTERS TO THE EDITOR. 
(The Editor does not hold himself responsible for opinions ex- 
pressed by his correspondents. Neither can he undertake 
to return, or to correspond with the writers of, rejected 
manuscripts intended for this or any other part of NATURE. 
No notice is taken of anonymous communications. | 
The Caucasus. 
I AM very reluctant again to trespass on your columns, but 
“J, W. G.’s” note, in NaruRE of April 8, leaves me no alterna- 
tive. It contains, at least, one assertion which ought not to pass 
uncorrected in any scientific journal. I refer to the following 
sentence :— 
“The fact that the Caucasian place-names are derived 
from different languages had not been overlooked; but the 
rules laid down by the R.G.S. Committee, to which Mr. 
Freshfield refers, admit the principle in such cases of accepting 
the spelling of a standard national gazetteer or of official 
survey maps.” 
In reply to this statement, I have to point out that the rules 
adopted and promulgated by the Royal Geographical Society in 
1891, and confirmed in 1894, say exactly the contrary. I quote 
the two rules applicable in the case of the Caucasus, which 
are those on which I have endeavoured to act. 
‘© The true sound of the word, as locally pronounced, will be 
taken as the basis of the spelling.” 
«Tn the case of native names in countries under the dominion 
of other European Powers in whose maps, charts, &c., the 
spelling is given according to the system adopted by that Power, 
such orthography should, as a rule, be disregarded, and the 
names spelt according to the British system, in order that ‘the 
