416 



NA TURE 



[August 30. 1888 



in English, a French abstract has been prepared by Prof. 

 Dewalque, the Secretary of the General Committee 

 on Unification of Nomenclature ; and copies of this 

 abstract will be distributed at the meeting. The English 

 Committee, under the presidency of Prof. T. McK. 

 Hughes, will also present its revised Report, which is 

 now being printed, .and forms a substantial work. 



Opportunity will be given on Tuesday afternoon for 

 visiting the British Museum, where the fine collections 

 illustrative of prehistoric archaeology will be examined 

 under the guidance of Mr. A. W. Franks. 



On Wednesday morning the sitting will be occupied 

 with the discussion of a subject which has of late years 

 been warmly debated in geological circles — the nature 

 and origin of the crystalline schists. Special authorities 

 on this subject have been invited to contribute short 

 memoirs which have been printed in advance. As copies 

 of these papers will be distributed to the members, the 

 communications may be taken as read and the time of 

 the meeting occupied only in their discussion. The 

 volumes of papers entitled " Etudes sur les Schistes 

 Crystallins," contains the following communications : — 

 " Les Schistes Cristallins," by Dr. Sterry Hunt ; '" Zur 

 Klassification der krystallinischen Schiefer," by Prof. 

 A. Heim, of Zurich ; " Sur la Constitution et la Structure 

 des Massifs de Schistes Cristallins des Alpes Occi- 

 dentales," by Prof. C. Lory, of Grenoble; "Bemerkungen 

 zu einigen neueren Arbeiten iiber krystallinisch-schiefrige 

 Gesteine," by Prof. J. Lehmann, of Kiel ; " Sur l'Origine 

 des Terrains Cristallins Primitifs," by M. Michel-LeVy, of 

 Paris; "The Archaean Geology of the Region North-West 

 of Lake Superior," by A. C. Lawson, of the Geological 

 Survey of Canada ; " On the Crystalline Schists of the 

 United States and their Relations," by various members 

 of the United States Geological Survey ; and a paper by 

 M. K. A. Lossen, of the Geological Survey of Prussia. The 

 group of papers contributed by the United States Survey 

 contains first an " Introduction," by Major J. W. Powell, 

 the Director, followed by a paper on " The Crystalline 

 Schists of the Lake Superior District," by the late R. D. 

 Irving, and T. Chamberlin and C. R. Van Hise ; this is 

 succeeded by a sketch of " The Crystalline Schists of the 

 Coast Ranges of California," by G. F. Becker, and a brief 

 description of " The Crystalline Rocks of Northern Cali- 

 fornia and Southern Oregon," by Captain C. E. Dutton. 



Wednesday afternoon will be devoted to a visit to the 

 Natural History Department of the British Museum 

 where the visitors will be received by Prof. Flower, as 

 Director of the establishment. 



On Wednesday evening the Congress will be received 

 by Dr. A. Geikie, as Director-General of the Geological 

 Survey, at the Museum of Practical Geology in Jermyn 

 Street. With the view of illustrating the subjects that will 

 have been discussed at the morning sitting, it is proposed 

 that during the evening a series of microscopic sections 

 showing the structure of the crystalline schists shall be 

 exhibited on the screen, by means of the lime-light, in 

 the theatre of the Museum. 



At 10 o'clock on Thursday morning the Congress will 

 re-assemble in the University theatre, and proceed to 

 the discussion of questions bearing upon the International 

 Map of Europe. The Map Committee will present its 

 Report, and exhibit specimen sheets illustrating the 

 character of the work. In the afternoon the members 

 will make excursions in various directions. One party 

 will visit Windsor and Eton, where they, will be enter- 

 tained by the masters of Eton College ; another party 

 will visit Kew, and be received by Mr. Thiselton Dyer, 

 as Director of the Royal Gardens ; other members will 

 go down the river to Erith and Crayford for the purpose 

 of examining the brick-earths and gravels of the Thames 

 valley ; while otheis will probably visit Watford and 

 St. A'bans. 



At the meeting on Friday morning the discussion on 



nomenclature and classification, and on the coloration 

 of maps, will be resumed. In the evening there will be 

 a reception at the rooms of the Geological Society at 

 Burlington House, by Dr. W. T. Blanford, as President 

 of the Society. An evening reception, the date of which 

 is not yet fixed, will also be held by Prof. Prestwich, the 

 President of the Congress. The concluding business of the 

 Congress, mostly of a formal character, will be taken at 

 Saturday morning's sitting. 



By permission of the Council of the Zoological Society, 

 the Society's Gardens in Regent's Park will be open free 

 to members of the Congress, not only during the week of 

 the meetings but (after 1 o'clock) on Sundays, September 

 16 and 23. 



Several geological excursions have been organized for 

 the week following the London session. One of these, 

 which promises to be extremely popular, is to the Isle of 

 Wight, under the direction of Messrs. W. Whitaker, 

 J. Starkie Gardner, A. Strahan, and H. Keeping. By 

 invitation of Sir Charles Wilson, this party will also visit 

 the offices of the Ordnance Survey at Southampton. An- 

 other interesting excursion is to North Wales under Dr. H. 

 Hick?, assisted by Prof. J. H. Blake for Anglesey, and by 

 Mr. G. H. Morton for the Carboniferous Limestone of 

 Llangollen. A third excursion is planned to East York- 

 shire, under the direction of Mr. T. W. Woodall and Mr. 

 C. Fox-Strangways, assisted by Mr. W. H. Hudleston, 

 for some of the Colitic series. Mr. G. H. Lamplugh for 

 the Flamborough Chalk, and Mr. Hugh Bell, for the 

 mines and iron-works of Middlesborough. West York- 

 shire will also be visited bv a partv under the guidance of 

 Mr. J. E. Marr and Mr. R H. Tiddeman. Finally, an 

 excursion to East Anglia has been organized under Mr. 

 F. W. Harmer (Mayor of Norwich) and Mr. Clement 

 Reid, assi-ted for the older Pliocene beds of Suffolk by 

 Dr. J. E. Taylor, of the Ipswich Museum. A guide-book 

 containing geological descriptions of the localities about 

 to be visited, written in French and illustrated by 

 coloured geological maps, is in course of preparation, and 

 will be presented to the members of the Congress. To 

 this guide-book Mr. Topley has contributed a sketch of 

 the geology of the various railway routes by which 

 foreigners will reach London. 



The great interest taken in the forthcoming meeting is 

 attested by the fact that already between 500 and 600 

 members have been registered. The list includes nearly 

 all the most distinguished geologists on the Continent 

 and in America, many of whom will arrive in time to be 

 present at the Bath meeting of the British Association 

 during the week preceding the opening of the Congress. 

 It is known that many of these geologists will bring with 

 them collections of minerals, rocks, and fossils, for exhibi- 

 t'on in the temporary Museum which will be formed in 

 the library of the University of London, and which 

 promises to be one of the most interesting features of the 

 meeting. On the whole, there can be no question that 

 the success of the forthcoming session of the Congress 

 is abundantly assured. 



MODERN VIEWS OF ELECTRICITY} 



Part IV.— Radiation. 



x. 



IT AVING now described a possible method of measur- 

 ■*- -*- ing the velocity of electric wave propagation, and 

 therefore of at least the ratio of the two ethereal constants 

 k and ft, by an experiment on the different parts of one 

 enormously large and properly chosen circuit : return to 

 the consideration of the ordinary small discharging 

 Leyden jar or other alternating current circuit of a 

 moderate size, it may be a few yards or a foot or an inch 

 in diameter. 



If the alternating currents are produced artificially 



^Continued from r. 393. 



lly bv 



