436 
WA TORE 
[ Sept. 10, 1885 
o1igin has apparently received confirmation in the case 
of another substance. 
But although we have chiefly confined ourselves to the 
spectroscopic bearing of the work, it is not too much to 
say of it that, if this separation be in the sense as indi- 
cated, it is the most important work in mineral chemistry 
we have had for many years. By patient work the group 
of cerium, didymium, &c., metals has yielded several new 
metallic oxides, differing considerably from didymium, 
but having the same general reactions, being members of 
the same group in fact. The difference in the ordinary 
chemical reactions of cerium, lanthanum, didymium, 
scandium, terbium, ytterbium, and probably samarium is 
generally very slight, and they can only be separated by 
long-continued operations, nearly always cases of frac- 
tional separation. The close relationship of these metallic 
oxides has been long recognised, and the group has been 
considered peculiar in this respect, and in consequence 
an immense amount of labour has been expended upon 
it, more than has ever been expended on groups of other 
metallic oxides. Indeed, the notion that heat is the agent 
of chemical resolution seems to have gained such a hold 
that apparently for the last two, or three, decades, with 
the exception of the cerite metals, it is the only reagent 
the action of which has been taken as definitive in esta- 
blishing a thing to be an element. We are not aware 
that any records of patient work on chromium exist, 
attempts to isolate any other substance from chromium 
oxide other than our ordinary chromium. The general 
properties of this, or these, oxides surely invite to further 
investigation. And in the case of nickel and cobalt 
which appear almost to be isomers, there is a fine field for 
investigation which might be as profitably cultivated 
perhaps as an almost infinite series of carbon compounds. 
OUR BOOK SHELF 
Annuaire géologique unive*).. et Guide du Géologie autour 
de la Terre. Par le Dr. Dagincourt. (Paris : Comptoir 
géologique de Paris, 1885.) 
THIS is the first annual issue of a geological guide edited 
by the Secretary to the Geological Society of France, 
which cannot fail to be of the greatest use as a book of 
reference to those concerned with geology all over the 
world. Multum in parvo would be a very suitable motto 
for the book, for the amount of information which it con- 
tains in a small space is really marvellous. The editor 
does not profess to have carried out the whole of the 
programme which he has set before himself in the present 
issue ; but it was decided to bring out the volume this 
year on account of the meeting of the Geological.Congress 
at Berlin, and also in order that he may be able in the 
ensuing issue to profit by private and public criticism. 
The best criticism of it will be a bare statement of its 
contents. It first describes the history, various meetings 
and utility of the Congress of Geologists, with the pro- 
ceedings at the meetings in Paris and Bologna. It then 
takes the continents in alphabetical order, and the countries 
in them in the same way, and supplies a mass of geological 
information of all kinds with regard to each. Taking 
as an example the first country under the head Europe, 
which is Germany (Allemagne), we find a list of books on 
the bibliography of German geology, of general (as dis- 
tinguished from special and detailed) geological maps, 
and of the leading works on certain districts ; these are 
succeeded by a general sketch of the geological features 
of Germany, and of the occurrence of the various 
geological systems';{then a detailed?account of the organisa- 
tion for the production of geological maps in the various 
countries and provinces composing the German Empire ; 
then a sketch of the institutions in which geology is 
taught, the various universities with their professors, 
laboratories, collections, museums, &c., the professors at 
the various polytechnic and agronomical schools, the 
public and private geological collections, with in some 
cases, brief descriptions of the principal features (these 
occupy a considerable space), then the various geological 
societies, with their organisations; next the periodical 
publications, their prices, size, general nature of the con- 
tents, divided into five classes—(1) those specially geo- 
logical, (2) those containing from time to time geological 
papers, (3) geographical periodicals containing geological 
papers, (4) those devoted to mining, (5) collections of 
geological and paleontological memoirs. These lists are 
succeeded by others which form a very important feature 
of the work—viz. the names, addresses, and special fields 
of all the geologists in the German empire ; and finally 
the titles of all the books and papers which have appeared 
during the past year on mineralogy, petrography, geology, 
and paleontology, arranged in alphabetical order. This 
description of the volume under the head “ Allemagne,” 
will give an accurate idea of the scope and arrangement 
of the book, for although circumstances have prevented 
the scheme being carried out with the same degree of 
thoroughness for every part of the globe, the volume will 
year by year approach nearer to, doubtless even improve 
upon, this standard. In the case of Great Britain, for 
instance, the issue for 1886 will contain a thorough study 
of our geology, and its teaching in our universities and 
other public institutions. Its ultimate completeness must 
naturally depend much on the assistance which the editor 
receives from geologists all over the world in supplying 
information, making the necessary alterations required by 
time, offering suggestions and adding corrections ; and 
the volume is so useful and full in design that we have 
little doubt Dr. Dagincourt’s fellow-geologists will willingly 
help him to carry it out in all its details. We observe 
that Tasmania has by an error been put amongst Asiatic 
countries instead of in Australasia. 
LETTERS TO THE EDITOR 
[The Editor does not hold himself responsible for opinions expressed 
by his correspondents. Neither can he undertake to return, 
or to correspond with the writers of, rejected manuscripts. 
No notice ts taken of anonymous communications. 
[The Editor urgently requests correspondents to keep their letters 
as short as possible. The pressure on his space is so great 
that it ts impossible otherwise to insure the appearance even 
of communications containing interesting and novel facts. | 
The Meteoric Cycle and Stonehenge 
WE are now passing through the hundredth meteoric cycle of 
nineteen years, which commenced with a.p. 1882, and will 
terminate with A.D. 1900. These cycles began with the year of om 
Saviour’s birth, and our prayer books contain tables showing for 
many successive years on what days Easter days and our 
movable festivals will occur. At the end of every such cycle 
the new and full moons happen within an hour and a half of the 
same time of the year as they did at the beginning. 
With these cycles is commonly associated the name of Meton, 
an astronomer of Athens, who wrote a book on the subject, by 
which the Greeks regulated the recurrence of their festivals. 
He flourished 432 years B.C. But the knowledge of these cycles 
existed in England centuries before the time of Meton, as I will 
presently show, and it is probable that the four very ancient 
erections supposed to have been temples of the sun near 
Penzance, had reference to this cycle of nineteen years, as they 
each consisted originally of nineteen stones placed upright and 
rising from 3 to 6 feet above the ground in rude circles varying 
in diameter from 65 to 80 feet. These temples are still existing, 
although some of their stones have fallen, and they are miles 
from each other, but are all called in the printed maps, as well 
as immemorially, by one and the same name, viz. ‘‘ Vine 
