Fesruary 18, 1897 ] 
NATURE B63 
story of Croll’s life, as all too shortly told by himself, and 
supplemented by Mr. Irons, is one of deep pathos. 
Of his character, deeply impressed by the truths of 
religion, Calvinistic, conscientious to a degree, possessed 
of the most inflexible power over himself, not hesitating 
to subject himself to severe and long-continued physical 
suffering when he thought it his duty, full of generosity 
in assisting other inquirers after truth, we obtain many 
glimpses in the volume before us. 
Of Croll’s scientific work, which bears at once the 
impress of genius, metaphysically acute, and of imperfect 
knowledge, the result of unsystematic training in physics, 
it is more difficult to form a just estimate. It was so 
controversial, and dealt with matters on which the final 
judgment of science has not yet been passed. That 
which he regarded as his most important and most con- 
clusive work in physics—his glacial theory—has been 
steadily losing ground among geologists and physicists 
alike, and now it finds difficulty in securing a champion 
to fight its battles. His work on ocean currents seems 
more likely to be permanent, for he did much to call 
attention ,to the paramount importance of winds in 
determining oceanic circulation, although he doubtless 
pushed the argument somewhat too far against Carpenter, 
the advocate of the temperature theory ; yet the very 1m- 
perfections of his work bear the strongest testimony to 
the inherent suggestive genius of the man. That one 
whose knowledge of elementary physical principles was 
so confused as appears from some of the correspondence, 
e.g. that on pp. 452-458, should have been able to sway 
contemporary scientific opinion on physical subjects was 
marvellous, and was due, not only to the extraordinary 
suggestiveness of his mind, but also to his metaphysical 
power. By long-continued meditation, the different 
parts of his theory became in his mind so closely con- 
nected together, analogies became so clearly perceived, 
so unconsciously magnified, that difficulties faded into the 
background, or, even in his fertile mind, were made to 
yield new reasons for his conclusions. Yet, through all, 
the transparent sincerity of the author, and his evident 
devotion to truth were as clear as his absolute conviction 
of the necessity of his own conclusions ; and thus, as well 
as by his remarkable power of logical exposition, he 
imbued the reader with his own confidence, and this the 
more readily in the case of the glacial theory, because 
the grandeur and simplicity of the explanation, if it did 
not afford some presumption of its truth, at least created a 
prejudice in its favour. 
But though Croll’s position will doubtless be deter- 
mined by his work in physics, he would himself have 
chosen to be judged by his metaphysical writings. If we 
may judge from the summaries in the work before us, as 
well as the correspondence from Principal Cairns and 
others, these works were of striking, though by no means 
of transcendent, merit. 
The book is well printed and got-up. To one who did 
not know Croll personally, it seems that some of the 
correspondence might have been omitted with advantage, 
It is, however, an ungrateful task to criticise what has 
been a labour of love. The last words of the preface 
are: “It may be added that the entire proceeds of the 
sale will be devoted to Dr. Croll’s widow.” 
Babs C. 
NO. 1425, VoL. 55] 
ELEMENTARY METEOROLOGY. 
Elementary Meteorology for High Schools and Colleges. 
By Frank Waldo, Ph.D., late Junior Professor in the 
U.S. Signal Service. Pp. 4 + 373. (New York: 
Cincinnati, Chicago American Book Co., 1896.) 
ge writing an elementary treatise on meteorology, there 
are two very evident errors which an author may 
commit. There is the danger of producing a book which 
is reduced to such simplicity that it becomes wearisome 
or even needless, because it contains many facts which 
are either of ordinary experience or have been learnt 
from other branches of elementary physics. And on the 
other hand, there is the difficulty, common to all element- 
ary works, of knowing where to stop. To the adept, 
many facts and deductions, which appear perfectly simple 
and worthy of attention, are stumbling-blocks to the 
beginner and become sources of annoyance to the reader. 
In looking through this book one learns that there are 
other difficulties which need to be avoided, and though 
Dr. Waldo has to some extent avoided the big pitfalls by 
steering clear of childish repetition on the one hand, and 
injudicious overloading on the other, he has not been so 
successful in recognising the necessity of accuracy of 
expression and clearness of explanation, One might, 
too, take a preliminary objection to the choice of the 
readers to whom this book is addressed. Dr. Waldo 
admits in his very first paragraph that the “science is 
as yet but partially developed, and much that is at present 
accepted as fact will be modified by future investigations.’ 
The question naturally arises, is it desirable to place 
before students explanations that are admittedly im- 
perfect, and to devote the time that might be well spent 
in accurate training to the acquisition of an amount of 
ill-digested information, that does not in all cases even 
satisfy those with whom the information has originated ? 
Of course, no blame rests with Dr. Waldo on this score. 
If those who are responsible for education in America 
are determined to press some acquaintance with meteor- 
ology in its present condition on their pupils, it is clearly 
the duty of experts to supply the best text-books in their 
power, so that the least possible injury be effected. Of 
Dr. Waldo’s capacity and intimate acquaintance with the 
subject of which he treats, there is no question. But he 
does not always exhibit sufficient care to place his facts 
in the clearest possible light, so as to be of the greatest 
possible assistance to the student. As an illustration of 
this carelessness, we may take the sentence on page 30, 
beginning, “ The heat received by the water surface warms 
it but slightly.” This expression, as it stands, would mean 
that the surface of the water is but slightly warmed, and 
the explanation that follows would be incorrect; but 
what is really meant is that the whole mass of water is 
but slightly warmed by the sun’s rays. Such looseness 
of expression must be very confusing toa student. Take 
another instance. It is stated (p. 21), “Our earth, in 
its revolution round the sun, intercepts less than one-half 
of a millionth of the whole amount of heat given off by 
the sun.” Why are the words “in its revolution round 
the sun” introduced? These words obscure the real 
point at issue, which is, or should be, the comparison 
of the area of the sphere whose radius is the sun’s distance 
from the earth, with the space the earth occupies in that 
