Aug. 14, 1873] 
THE LAST GLACIAL EPOCH 
Cun the Cause, Date, and Duration of the Last Glacial 
Epoch of Geolozy, and the Pretable Antiquity of Man, 
With an investigation and description of a new move- 
ment of the Earth. By Lieut.-Colonel Drayson, R.A., 
F.R.A.S. (London: Chapman and Hall, 1873.) 
"THE author of this work allows the existence of the 
motion of rotation of the earth on its axis and its 
revolution round the sun. That motion, however, of the 
axis of the earth, to which is due the precession of the 
equinoxes, is to him a great stumbling block. He denies 
the possibility of this motion as generally accepted, and 
gives us a theory of his own, which is very novel, and the 
results of which are startling in the extreme. 
Lieut.-Colonel Drayson either knows nothing of 
dynamics or despises the science: the one key he 
makes use of to unlock the secrets of astronomy 
is geometry; he does not believe in the existence 
of a change in the plane of the ecliptic, and apparently 
is not aware that the attractions of the other planets on 
the earth mist produce periodic changes in the plane of 
the earth’s orbit. In consequence of this he persuades 
himself that all astronomers teach (and perhaps believe) 
that while the pole of the earth is describing a circle 
round the pole of the ecliptic, the obliquity of the ecliptic, 
which is the angular distance between these poles, is con- 
stantly changing. He calls this a geometrical impossi- 
bility, and nobody would hesitate to agree with him that it 
is ; but astronomers would at once deny that they either 
teach or believe anything of the kind. The popular be- 
lief is that the pole of the earth describes a circle of 
radius 23° 28’ round the pole of the ecliptic as a centre, 
and that the whole circle would be described in something 
Over 25,000 years, 
Lieut.-Colonel Drayson tells us that the true motion 
of the pole of the earth is in a circle whose radius 
is 29° 25' 47”, and whose centre is at a distance of 
6° from the pole of the ecliptic. He attempts to prove 
this, and, we believe, has succeeded in persuading 
himself that he has proved it. He does this by show- 
ing that this particular circle will satisfy all the neces- 
sary conditions, as he puts them, and also (we as- 
sume) as he understands them. The author next pro- 
ceeds to deduce the consequences of this motion. His 
circle would be described in 31,840 years, so that at inter- 
vals of 15,920 years the obliquity of the ecliptic would 
vary as much as 12°. The consequence of this would be 
that about 13,700 B.c., Great Britain would have had 
during the winter an arctic climate, the sun in lat. 54° 
not being 1° above the horizon at the winter solstice, and 
during the summer a tropical climate. This is supposed 
to have been the last glacial epoch, and the author has 
such confidence in his theory that he promises us glacial 
epochs every 31,840 years. 
The book, as a whole, we look upon as most unsatis- 
factory. Had the author mastered the principles of 
dynamics, he probably would not have been led by a 
mistaken interpretation of movements which he only 
partly understood, into the fatal error of attempting to 
solve one of the most abstruse problems in astronomy by 
mere geometry, The days of such attempts were, we 
hoped, past for ever, 
NATURE 301 
The motion of the earth’s axis is well illustrated by the 
motion of a boy’s top when it is spinning with its axis in- 
clined to the vertical. Every one has seen a top while 
spinning on its own axis, revolve round the vertical with 
approximately constant speed, while its axis remained 
inclined to the vertical at an approximately constant 
angle : but who has seen a top spinning so that its axis 
revolved with constant speed round a line inclined to the 
vertical at an angle of 6°, or any other angle? Till 
Lieut.-Colonel Drayson produces a top which will do this, 
thereby proving experimentally that such a motion is 
possible, or till he demonstrates by analysis the possibility 
of such a motion, we shall feel confident in rejecting his 
theory of the earth’s motion, as the theory of a para- 
doxer, and in regarding the cause of the last glacial 
epoch as a secret still unknown. 
DR. SMITH ON FOODS 
Foods. By Edward Smith, M.D., F.R.S. 
King and Co.) 
bs ia tendency during the last thirty years or so to the 
equalisation, throughout the country, of the prices 
of the several articles employed as food, has done much 
to make the subject of Foods one of much greater inte- 
rest to a larger class ef the community than heretofore. 
The products of a district being now scarcely, if at all, 
cheaper than those that can be obtained from a consider- 
able distance, a knowledge of the relative nutritive value 
of foods becomes essential to a larger number. We 
therefore look with great interest to the results of Dr. 
Edward Smith’s considerable experience, especially with 
regard to some of the articles of more modern intro- 
duction. 
The classification adopted is the following. Foods are 
first divided into solid, liquid, and gaseous, an arrange- 
ment which has the disadvantage of separating closely- 
allied substances from one another, milk having to be 
considered removed from cheese and butter. The solid 
foods are then divided into animal and vegetable, and 
each of these are subdivided into nitrogenous and non- 
nitrogenous. The source, composition, and alimentary 
properties of each article are then discussed in detail. The 
analyses are mainly those of Fresenius, Frankland, 
Wanklyn, and other well-known chemists. The author 
in most cases is able to introduce the results of his own 
observations on the physiological action of each sub- 
stance, which are also to be found in the Transactions ot 
the Royal Society. Taking arrowroot as a fair example 
of the manner in which the subject is treated, after a short 
account of its origin we find that “the proximate elements 
in 100 parts are water 180, and starch 82'0; so that it 
is or should be free from nitrogen. There are 2,555 
grains of carbon ini lb, ... Ten grains of arrowroot when 
thoroughly consumed in the body produce heat sufficient 
to raise 10°06 lbs. of water 1° F., which is equal to lifting 
7,766 lbs. one foot high.” The author observes that when 
eaten alone on an empty stomach it gives no sense of 
satisfaction, but one of malaise. Eating 500 grains in- 
creased the emission of carbonic acid o°154 grains per 
minute. The rate of respiration was somewhat lessened, 
and the pulse was increased four beats per second (sic). 
As each subject is similarly described, it is evident that 
(Henry S. 
4.7 em’ 
