'AucusT 29, 1912 | 
NATURE 
665 
He then continues :— 
The propagation of Light occurs, as we have 
already seen, by dynamical undulations, for so we 
call the uninterrupted alternation of the opposing 
forces. This view stands between the Undulatory 
theory which Huygens and Euler taught and the 
Emanation theory of the Newtonian school, almost 
in the same way as the dynamical theory of Heat 
between the mechanical and electrical theories. 
Schelling, in his Weltseele, has recognised the possi- | F 
| work on the subject. 
bility of such a view. 
Besides these extracts from the ‘Ansicht 
der chemischen Naturgesetze,” Oersted  ex- 
pounded his theory of light in a_ particular 
communication which he made to the Royal 
Danish Society of Science, and of which an 
abstract is printed in its Proceedings for the 
year 1815-16, pp. 12-15. One sentence will 
suffice as a summary of this abstract :— 
According to the theory which has been set forth 
here, one may fairly well consider a ray of Light as 
a succession of immensely small electric sparks which 
might be called the elements of Light. 
It is evident that, with all his ingenious in- 
sight, Oersted was far from having formulated 
an electric theory of light in terms which would 
admit of verification. His perception that electric 
forces were called into play in the displacements 
of the luminiferous waves was obscured by the 
view which he held of conduction; for, surely, the 
condition of the quasi-elastic actions called forth 
in the propagation of light should have been that 
the forces or agencies at work must not attain 
so great a value as to produce a discharge, as 
we now understand it. Indeed, in the existing 
state of knowledge, when as yet the quasi- 
elasticity of dielectrics was unknown, the founda- | 
tion facts for an electric theory were not avail- 
able. The remarkable fact is that in the paucity 
of available facts his speculations took him so 
far as they did along the road of progress. 
Sirvanus P. THompPson. 
SCIENCE AND RESERVATIONS.! 
Aten a district interesting to geologist and 
: naturalist alike is handed over to a body 
of scientific investigators, the result in these days 
of intensive research is likely to be important. 
Dr. Conwentz, the indefatigable pioneer of nature- 
protection, has edited a volume of 700 pages, 
which gives the results of such a study in the 
case of the Plagefenn at Chorin, in Prussia, a dis- 
trict of marshes, lakes, islands, and wooded 
country. Of course, there are gaps in the mass 
of knowledge accumulated during several years, 
in the fauna and lower flora, for instance. But 
the whole work is a remarkable study in classifica- 
tion and generalisation. 
The relations of water and earth, for which the 
historical records of the district are very useful, 
have seldom been studied so minutely, especially in 
1 “ Beitriige zur Naturdenkmalpflege.” Herausgegeben von H. Conwentz. 
Dritter Bznd—*‘Das Plagefenn bei Chorin.” Ergebnisse der Durch- 
forschung eines Naturschutzgebietes der preussischen Forstverwaltung, 
By H. Conwentz, F. Dahl, R. Kolkwitz, H. Schroeder, J. Stoller and 
E. Ulrich. Pp. xvi+688. (Berlin: Gebriider Borntraeger, 1912). Price 
18.75 marks 
NO. 2235, VOL. 89] 
Dies 
reference to the lower vegetation. 
| Schroeder describes the diluvial, and Dr. J. Stoller 
the alluvial, structure. On their foundations, Dr. 
E. Ulrich bases his botanical study. This, and 
the monograph on the fauna, are fine studies. As 
contributions to ecology they are of great value. 
Many readers should be able to obtain a better idea 
of the intricacies of plant communities from such 
a monograph as Dr. Ulrich’s than from a general 
The sociology of plants and 
animals, as conditioned and initiated by geological 
and meteorological forces, has still ali the fascina- 
tion of a young science. Excellent diagrams and 
maps illustrate the social processes, so well marked 
in this district, which Dr. Ulrich praises as a 
, model of biological complexity and natural beauty. 
Professor Kolkwitz’s essay on the plankton is 
placed at the end of the volume, but should be 
read with Dr. Ulrich’s contribution. 
The account of the fauna could not have been 
in better hands than in those of Prof. F. Dahl. 
His general introduction on metheds of research 
and his conclusions on the relations between animal 
and plant communities are fresh and important. 
The analytical lists are carefully executed; that 
of the fauna extends to more than 200 pages. The 
index is a good one. 
The keynote of the whole study, and the point 
of departure and of arrival alike, is the coast-line 
of a fresh-water lake; and there are few more 
interesting sites for the study of organic life. Our 
own country, it may be observed, has an abun- 
dance of similar districts, more or less useless to 
the agriculturist, but of enormous value for 
scientific research. A. E. CRAWLEY. 
NOTES. 
ARRANGEMENTS have been made for the inclusion of 
two organised discussions in the proceedings of 
| Section H (Anthropology) during the forthcoming 
| meeting of the British Association at Dundee. 
On 
Friday, September 6, a discussion on the ethnological 
aspects of Scottish folklore will be opened by Mr. W. 
Crooke, president of the Folklore Society, and papers 
will be contributed by Mr. E. S. Hartland, Mr. W. J. 
Brodie-Innes, and Canon J. A. McCulloch. On 
Monday, September 9, the president of the section, 
Prof. G. Elliot Smith, F.R.S., will read a paper on 
the distribution of megalithic monuments, in which 
| he will develop the theories as to the racial affinities 
of their builders which he has recently put forward. 
In the discussion which will follow, Prof. Ridgeway, 
Prof. J. L. Myres, Prof. W. Boyd Dawkins, Dr. T. 
Ashby, and others have promised to speak. 
THE summary of the weather issued by the Meteoro- 
logical Office for the week ending August 24 shows 
that the general conditions were again extremely un- 
settled over the United Kingdom as a whole, but in 
some localities in Scotland, Ireland, and the north-east 
of England rain is said to have been less common 
than elsewhere. The deficiency of temperature ex- 
ceeded 3° in most districts, and the south-west of 
England was the only district where the highest day 
