354 
Analyses of Books. fjune, 
the friCtion of the rotation of the stars, whilst terrestrial gravi- 
tation is transmuted into heat by the friction of the Earth’s 
rotation against those rays of light. “ In this case the light 
emanating from the Sun is caused by the same conflicting aCtion 
of solar gravitation which carries and gu'.des the Earth in its 
orbit.” 
We may here remark that the experiments made for the 
reciprocal transformation of gravitation, and the so-called phy- 
sical forces or modes of energy, have so far led to no decisive 
results. 
In Part XIII. it is suggested that if the rotation of the Earth 
were more rapid, its aCtion would carry everything lying loosely 
on the Earth first to the Equator and then upwards. If it be 
true that the Earth’s rotation is being gradually retarded, the 
Earth may have passed through a phase similar to that of 
Saturn, and may once have had its belts. This chapter is 
accordingly headed “ A Belt of Boulders.” But is it in evidence 
that such belts exist on a parallel to the Equator to a greater 
extent than in other regions of the Earth’s surface ? 
Mr. Jordan considers that the obliquity of the ecliptic to the 
Equator depends not on cosmical, but “ on local terrestrial causes 
which determine the plane of rotation, and have frequently 
changed that plane.” We doubt, however, very strongly, whether 
any such changes would account for the epochs of glaciation and 
for the genial climate of the earlier Miocene. 
We have thus presented a brief, and we trust not unfair, view 
of the author’s main ideas, for the demonstration of which we 
must refer to the work itself. 
An Introduction to Practical Organic Analysis. By G. E. R. 
Ellis. London : Longmans, Green, and Co. 
This is a very small book for so wide a subjeCt as organic 
analysis. It will, however, be at once seen that the author gives 
instructions merely for the recognition or detection of certain 
organic bodies, and not for their quantitative determination. 
Thus what is perhaps too conventionally known as organic 
analysis, the d’etermination of the four principal organic 
elements by combustion, is conspicuous by its absence. Num- 
bers of organic compounds also — we may especially mention the 
colouring-matters — have not fallen within the author’s plan. 
Still we must admit, with some surprise, that considering the 
very limited compass of the treatise the author has contrived 
