144 
NATURE 
[ FEBRUARY 3, 1923 

tropic minerals are arranged vertically in the order of 
their birefringence indicated in the central column ; 
and laterally from the centre outwards, according to 
their refractive indexes shown at the top of the table. 
The range of the refractive index of each mineral 
is given by a horizontal line, somewhat in the 
same manner as in the “ Petrographic Methods” of 
Dr. Holmes. 
Comparatively little use is made of the optic axial 
angle, though even a rough estimate involving no 
elaborate procedure or calculations may be quite useful. 
Another observation which can be made without 
difficulty is whether the direction of maximum absorp- 
tion coincides with the fast or the slow direction of 
vibration. The sections dealing with the felspars, 
pyroxenes and amphiboles are excellent, but the use 
of the term melatope (p. 32) for the point of emergence 
of an optic axis in interference figures should have been 
explained. 
The concluding pages are devoted to the author’s 
new quantitative classification of igneous rocks, which 
is based on the “ mode,” the actual minerals present, 
instead of on the “norm.’’ Most petrologists in this 
country believe, however, that any quantitative 
system of classification is essentially misleading. 
J. W. Evans. 
Annuaire pour lan 1923 publié par le Bureau des 
Longitudes. Pp. vilit+654+A118 + Br2+C16+ D72. 
Supplément 4 l’Annuaire du Bureau des Longitudes 
pour l’an 1923: Distribution des pluies en France. 
15 planches. (Paris: Gauthier-Villars et Cie, n.d.) 
6.50 francs. 
Tus very handy little volume is now widely known, 
and the issue for 1923 shows no falling off in its general 
utility ; it contains all the usual calendar information, 
and has tables and descriptive matter dealing with all 
classes of heavenly bodies ; there are also physical, 
mensurative, and geographical tables. The only point 
in these tables that seems to call for some criticism is 
the section relating to comets. The orbits given are in 
many cases by no means the latest or most accurate 
available ; the latest return of Encke’s referred to is 
that of 1914, though it has been seen since then, in 1918 
and 1921. The date given for the perihelion passage of 
the comet Pons-Winnecke in 1921 is June 20, which is 
eight days too late ; it is also curious that this comet is 
called simply Winnecke’s, forgetting that it was first 
found by the French astronomer Pons, and that its 
periodicity was known long before Winnecke found it in 
1858. 
The special essay contained in this volume is by 
M. G. Bigourdan on the climate of France ; it contains 
many tables and diagrams, and discusses the different 
types of climate belonging to different regions, and also 
the diurnal and annual variations in cloud, rain, ete. 
M. Bigourdan describes the system of weather forecasts 
by wireless, which are now distributed daily, and should 
be of great service to agriculturists. 
There are obituary notices of Gabriel Lippmann and 
Jules Carpentier, both of whom died last year. 
The small suggestion may be made that the leaves of 
the book should be cut, as is usually done in volumes of 
this character, where ease of reference is a desideratum. 
3 aul Os ol Dal Op 
NO. 2779, VOL. II1| 
| on soils, as might be expected from the head of a 

Common Stones: Unconventional Essays in Geology 
By Prof. G. A. J. Cole. (Common Things Series.) 
Pp. 259. (London and New York : Andrew Melrose, — 
Ltd., n.d.) 6s. net. 
Pror. Corr’s twenty essays*on common stones are 
written with a literary grace and charm which should 
give this book a firm place among British popular 
presentations of science. It should do to-day the 
service which Kingsley’s ‘‘ Town Geology ” did for an 
earlier generation. The volume sketches the modern 
theories of rock formation, on which the author writes 
with the knowledge of an expert, while his references 
to the field occurrence of the rocks make the reader 
share with him the pleasure of many field days. The — 
chapters which deal with sedimentary petrology are 
especially useful ; one of the most attractive is that 










































Geological Survey which has devoted especial attention 
to agricultural geology. 
Advanced students would profit by reading these 
essays, for they quote much new information and many 
unfamiliar instances; the author, for example, lays 
stress on the origin of oolitic structures by chemical 
processes, and on the formation of corries by nivation 
instead of by glacial erosion; he rejects some con- 
clusions based on the low ash content of anthracite ;— 
in emphasising the need for safeguarding our future 
coal supplies he remarks wittily that a century hence 
a chapter on coal would be out of place in his volume, 
as coal would then be regarded as a precious and not 
as a common material. 
The humanistic feeling shown in this book by its 
high literary quality and its frequent reference to the 
early founders of geology would ‘make its perusal of 
special benefit to science students in view of the grow- 
ing specialisation in their preliminary education. 
Kincardineshire. By the late George H. Kinnear. 
Pp. xi+122. (Cambridge: At the nie 
Press, 1921.) Price 4s. 6d. net. 
KINCARDINESHIRE, though one of the smaller of the! 
Scottish counties, is a compendium of Scottish geo- 
graphical types, for it includes typical areas of high- 
lands, lowlands, and of the eastern coastal districts. 
Kincardine is interpreted as ‘“‘the end of the high 
lands” and it is used for various localities in Scotland ; 
the name is appropriate to this county, as it includes 
the eastern end of the Grampians. The chief lowland 
area is the plain known as “ the Howe of the Mearns ” 
which is the eastern end of the Vale of Strathmore. 
The coast is very variable in character, and unusually 
picturesque ; part of it consists of soft beds which 
are undergoing rapid abrasion by the sea; elsewhere 
occurs an alternation of hard rocks which project in 
headlands such as that surmounted by Dunnottar 
Castle, and of soft bands which have been worn back 
into bays. The interest of the coastal scenery is 
enhanced by the numerous stacks and caves. The 
headlands act as groynes, and their protecting effect 
was shown in the case rendered classic by Lyell, who 
recorded the destruction of the village of Mathers 
on a single night in 1795 owing to the sea breaking 
through a ledge of limestone which had been weakened 
by quarrying. Fishing villages are numerous along 
