260 Notices of Books. [April, 
cause soever, their re-introdudlion is a difficult task. The Ice- 
land nightingales are probably due to the imagination of the 
poets to whom Professor Pilar appeals. We can scarcely sup- 
pose a bird of such limited powers of flight able to cross the 
wide and stormy seas which intervene between Iceland and 
either Norway or Scotland. In his hypothesis of a deluge every 
10,500 years, proceeding alternately from the north and from 
the south, M. Adhemar not only assumes the existence of 
polar ice-caps larger than observation justifies, but takes for 
granted that they rest upon the bottom of the ocean. Nor is the 
supposition of one unbroken ice-cap covering the whole of 
Northern Europe scarcely tenable in the face of the observations 
of Mr. Mattieu Williams.* Whilst fully admitting also that 
submergence and emergence have alternated over many, if not 
all, parts of the surface of our globe, can we recognise the pro- 
bability of a universal deluge, previous to which the preponder- 
ance of water was in the northern hemisphere, having occurred 
less than 10,000 years ago. All that we know of the distribution 
of organic life, as well marine as terrestrial, seems to point to 
the conclusion that for a very prolonged period land has predo- 
minated in the northern hemisphere and water in the southern. 
A Treatise on the Cycloid and all Forms of Cycloidal Curves. 
By Richard A. Proctor. London : Longmans and Co. 
1878. 
This is a work or two hundred and fifty pages, devoted to the 
investigation of a family of curves which have lost most of the 
interest which formerly attached to them, and which, so far as 
they are worth knowing, are studied with far greater ease and 
perspicuity by the analytical method. The mass of details of 
which the book is composed is hardly relieved by any real 
generality in treatment in spite of the parallel sequence of the 
propositions relating to the different curves. An effort is made 
at the close of the work to exhibit a problem in whose solution 
a knowledge of the properties of the cycloid is capable of appli- 
cation ; but even the approximate solution of Kepler’s problem 
there given fails to account for the fadt that “ students at the 
Universities ” are expedted to find the work of “ use.” 
The plates, which are due to Mr. Perigal and Mr. Boord, are 
excellent. The beauties and variety of these curves, together 
with the ease of their mechanical description, will always make 
them favourites with the amateur turner ; but the interest of the 
mathematician is soon satisfied with noting the effedt of changes 
in the mode of their generation on their form, without enquiring 
* Quarterly Journal of Sciencedvol. vii., p. 537. 
