August io, 1893J 



NATURE 



345 



recent petrographical research," a subject which Mr. 

 Teall has almost made his own. Papers are expected on 

 East Africa, the new red sandstone of the Midlands, the 

 igneous rocks of Derbyshire, the boulder clays and drifts 

 of the Midlands, the methods and need of teaching 

 geology both as a branch of education and as a valuable 

 training to engineers, miners, and others. Sections C and 

 D will jointly discuss " Fossil and Recent Coral Reefs," 

 both in respect to their origin and in relation to the part 

 which corals have played in the formation of the earth's 

 crust. Sections C and E will also hold a joint meeting 

 for considering the mutual relations of geology and 

 geography. 



In Section D Prof. Bohr, of Copenhagen, is expected 

 to communicate the results of researches of great import- 

 ance on the chemical process of respiration. A dis- 

 cussion will also probably take place on the question 

 how far the fundamental peculiarities of vital processes 

 admit of being explained as merely resulting from the 

 complication of the chemical and physical processes of 

 which they consist. It is expected that other moot ques- 

 tions of fundamental importance in biology will also be 

 brought under discussion. 



The President of Section E will treat in his address of 

 the Polar Basin, laying stress on some generally forgotten 

 facts and summarising our knowledge of the margin of the 

 Arctic Sea. Mr. W. M. Conway will give an account of 

 his mountaineering experiences in the Karakorum 

 Range. Messrs. Bruce, Burn-Murdoch, and Donald will 

 describe with photographs and paintings the scientific 

 results of a recent sealing expedition to Antarctic waters. 

 Mr. Guy Boothby will describe his journey across Aus- 

 tralia from north to south. There will also be papers on 

 the influence of their geographical surroundings upon the 

 people of Northern India, by Mr. E. Henwood, and a 

 similar paper on the Congo Basin by Mr. Herbert Ward. 

 Mr. H. R. Mill will describe the physical geography of 

 the Clyde sea area, and the bathymetrical survey of the 

 English lakes, and Mr. B. V. Darbishire will contribute 

 a paper on some conditions of cartographic representa- 

 tion of distributions. 



In Section F the subject of the presidential address 

 will be " The Reaction in favour of the Classical Political 

 Economy." Papers are expected to be read for discus- 

 sion on the monetary situation by Profs. Foxwell and 

 Cunningham, on agricultural depression by Messrs. H. 

 H. Scott and L. L. Price, on corn averages by Mr. R. 

 Hooker, on Australian banking by Dr. C. Gairdner, on 

 Poor Laws by Dr. F. Wilkinson, on industrial arbitra- 

 tion by Mr. D. Schloss, on the employment of the unem- 

 ployed, on local industries and the history of Nottingham 

 lace by Mr. Frith and others. 



The arrangements for Section G have not been re- 

 ceived as yet, but the many promises received from 

 eminent English and foreign engineers to attend the 

 meeting leaves no doubt that the proceedings of this 

 Section will be of unusual interest. 



In Section H the subject of the presidential address 

 will be one special phase of man's development. The 

 papers and discussions in this section, always of a diver- 

 sified and popular character, promise to be of more than 

 usual interest this year. Dr. Hans Hildebrand, Royal 

 Antiquary of Sweden, contributes a paper on "Anglo- 

 Saxon remains, and the coeval ones in Scandinavia," 

 and it is proposed to make his communication the basis 

 of a general discussion, chiefly with the view of defining 

 the special characteristics of Anglo-Saxon remains in 

 this country as distinct from those of Celtic and Scandi- 

 navian origin. Another subject, also full of interest and 

 even novelty to English archsologists, is the recently 

 discovered prehistoric lake or marsh village near Glaston- 

 bury, which is to be brought before the section by its 

 discoverer, Mr. Arthur Bulleid. As the buried ruins of 

 this village are now being excavated on a larger scale than 



VO. 1 241, VOL. 48] 



during the previous summer, it is expected that the 

 amount of industrial remains, already of much archaeo- 

 logical value, will be greatly enhanced before the meeting 

 of the Association. It has therefore been suggested that 

 the reading of Mr. Bulleid's report of these researches 

 will be a good opportunity for the eminent archaeologists, 

 who have agreed to act as a committee of reference and 

 advice, to discuss the more sahent features of this remark- 

 able discovery, and to describe from different standpoints 

 its bearing on the early history of our country. This 

 method of dealing with such a discovery is eminently well 

 adapted both for furthering the objects of the Association 

 and for communicating valuable information to the in- 

 vestigators themselves ; and it is earnestly hoped that 

 the committee of experts will find it convenient to be 

 present. Nor do these interesting subjects by any means 

 exhaust the list of the forthcoming materials. Anthropo- 

 logy proper will come largely to the front, and will receive 

 special consideration in the president's opening address 

 to the section, as has been stated above. 



Among the more popular scientific communications, 

 the presidential address and the popular evening 

 lectures must take their place. The popular lecturers 

 are Prof. Smithells, who will describe and illustrate his 

 recent researches on "Flame;" Prof. Victor Horsley, 

 who will treat of " The Discovery of the Physiology of 

 the Nervous System ; " and Prof. Vivian Lewis, who will 

 lecture to the local working-men on " Spontaneous Igni- 

 tion." In connection with the last announcement it may 

 be noted that the introduction of the working-men's 

 lecture dates from the last meeting of the Association in 

 Nottingham. 



It will probably be possible to make a further com- 

 munication in our next issue, bringing forward the 

 announcement of the principal arrangements for work 

 and entertainment in a state more nearly approaching 

 completeness and finality. Frank Clowes. 



MA GNE TO- OP TIC ROTA TION. 



■pARADAY'S famous discovery of the rotation of the 

 -*■ plane of polarised light by passing the beam through 

 a piece of his heavy glass placed along the lines of force 

 of a magnetic field, was the starting point of the very 

 important department of science now known as electro- 

 optics. From this, as the first observed physical relation 

 between optical and magnetic phenomena, has come the 

 electromagnetic theory of light with all the magnificent 

 researches and discoveries which have marked its experi- 

 mental verification in recent years. I propose in the 

 present article to give a short account mainly of magneto- 

 optic rotation and the progress which has been made 

 towards its dynamical explanation, followed by a brief 

 discussion of some of the more intimately related 

 phenomena which have been brought to light by recent 

 investigations. It is no part of my plan however to 

 discuss the experimental methods employed in the 

 various researches referred to. 



In the first place the magneto-optic relation which 

 Faraday found is to be distinguished from the apparently 

 similar effect which is produced by passing plane polarised 

 light through a plate of quartz cut at right angles to the 

 optic axis, or through a solution of sugar or tartaric acid. 

 In the latter case the turning of the plane of polarisation 

 depends only on the positions of the displaced particles 

 of or in the elastic medium which forms the vehicle of 

 the wave, and not on their motions ; in the former 

 the effect is a result of the motions of particles of other 

 matter imbedded in or loading the surrounding ether. 



The following illustration is I believe substantially 

 what I have heard given by Lord Kelvin. Imagine two 

 elastic jellies, one bored full of small helical cavities, 

 either all right-handed or all left-handed, and having 

 their axes all in one direction ; the other having in it 



