September 27, 1906] 



NA TURE 



549 



<ation, and M. Ihinspii Miggcsls ihat the colours of spots 

 may eventually bo diffcronlinted by spectroscopic observ- 

 ations. 



Colours and Mac.xituuks oi- Double Stars. — It is a 

 fjenerally accepted statement that when the magnitudes of 

 I he components of a binary-star system differ considerably 

 ihcir colours are also very different; similarly a slight 

 <liflference in magnitude is usually accompanied by a 

 similarity of colour. 



Whilst preparing his recently published and valuable 

 memoir on the double stars of Struve's " Mensurie Micro- 

 metricae " Mr. Lewis has gathered striking evidence that 

 these statements are true, and in No. 373 of the Ohserv- 

 alory he gives a table of physical pairs, from which it is 

 seen that a gradual increase in the differences of magnitude 

 is accompanied by constantly increasing differences of 

 colour. A discussion of fifty double stars situated in the 

 southern hemisphere corroborates this evidence. 



Rotation Period of Jupiter's Equatorial Region. — In 

 No. 41 17 of the Astronomische Nachrichtcn Mr. Denning 

 publishes the rotation periods, derived from a number of 

 spots situated on the equatorial side of the southern equa- 

 torial belt of Jupiter, as determined by him at Bristol in 

 the years 1898 to 1905-6 inclusive. From the tabulated 

 statement given it is seen that the rate during 1905-6 was 

 several seconds slower than in previous years. During 

 1880-3 ''^s rotation period was from eighteen to twenty- 

 seven seconds shorter than during 1905-6. 



GEOLOGY AT THE BRITISH ASSOCIATION. 

 T T is only natural that the salient geological features of 

 the district in which the association meets should in 

 some degree influence the character of the papers pre- 

 sented to Section C. Yorkshire, being rich in glacial and 

 post-glacial problems, it is not surprising that special 

 attention was directed to the more recent episodes in the 

 earth's history. The presidential address dealt with 

 British drifts and the inter-glacial problem, and, after a 

 review of all the evidence bearing on the question, Mr. 

 Lamplugh pronounces that no proof of mild inter-Glacial 

 epochs, or even of one such epoch, has been discovered 

 during the examination of glaciated districts in England, 

 Ireland, and the Isle of Man. The " Middle Glacial " 

 sands and gravels of our islands afford no proof of mild 

 inter-glacial conditions or of submergence. In most cases, 

 if not in all, they represent the fluvio-glacial material 

 derived from ice sheets. Most of the fossiliferous beds 

 regarded as inter-glacial contain a fauna and flora com- 

 patible with cold conditions of climate, and, in the excep- 

 tional cases where a warmer climate is indicated, the 

 relation of the deposits to the Boulder-clays is open to 

 question. 



Prof. Kendall followed the president's address with a 

 full and comprehensive account of the general geological 

 structure of the country round York, and dwelt specially 

 on the glaciation of the Vale of York and the Cleveland 

 Hills. JDuring the meeting the members were enabled to 

 visit the York moraine and study the glacier lakes and 

 overflows in the eastern part of the county under the 

 guidance of Prof. Kendall. 



Other local glacial papers dealt with the Kirmington 

 Drift deposits, recent exposures of glacial drift at Don- 

 caster and Tickhill, post-glacial deposits at Hornsea, and 

 the plain of marine denudation beneath the drift of Holder- 

 ness. 



Contributions dealing with drift problems farther 

 afield were presented by Mr. F. W. Harmer, who con- 

 tinued his work on the glacial deposits of the east of 

 England, and in another paper he applied the brilliant 

 results obtained by Prof. Kendall in the Cleveland district 

 to support his theory regarding " Lake Oxford " and the 

 origin of the Goring Gap. 



The Rev. W. Lower Carter applied the same results to 

 explain a dry valley which had been a glacier-lake overflow 

 at Cwm-Coed-y-cerig, in South Wales, and gave a detailed 

 account of the local glaciers which formerly existed in the 

 valleys of the Usk and Wye. 



Mr. R. D. Oldham brought forward a criterion of 

 glacial erosion of lake basins, and Prof. J. W. Gregory 



NO. 1926, VOL. 74] 



initiated a discussion on the problems connected with the 

 Palseozoic glaciation of Australia, India, and South .'\frica. 

 He pointed out that in Australia we have evidence of three 

 horizons at which glacial beds occur, the Cambrian, the 

 Carboniferous, and the Pleistocene. The Cambrian glacial 

 beds near .Adelaide range 400 miles north and south, and 

 are interbedded with marine sediments containing a rich 

 Cambrian fauna. Evidence of Pleistocene glaciers has only 

 been found on the mainland near the summit of Mt. 

 Kosciusko, the highest mountain of Australia. The 

 Carboniferous glaciation is the most important, and pre- 

 sents points of the greatest interest. While in the State 

 of Victoria there exists undoubted evidence of land ice 

 riding over an irregular land surface, in New South Wales, 

 West Australia, and in India the glacial beds include some 

 that were laid down below sea-level. Beds presumably of 

 this age are also found in South Africa, South America, 

 and perhaps on the eastern flanks of the Urals. Prof. 

 Gregory pointed out the inherent probability of these beds 

 having formed part of a once continuous sheet of glacial 

 deposits. No proof is forthcoming that they were 

 synchronous, and in Africa and Australia the glacial 

 evidence disappears to the north, ending about the southern 

 tropic, and begins again in the northern hemisphere in 

 latitude 17° 20' N., increasing in strength northwards to 

 Cashmere. 



After a critical survey of the three theories which have 

 been advanced to explain this problem, viz. (i) the shift- 

 ing of the earth's axis (Oldham and Penck) ; (2) a universal 

 refrigeration of the world due to a change in the composi- 

 tion of the earth's atmosphere (Arrhenius) ; and (3) local 

 concentration of snowfall in consequence of a different 

 distribution of land and water. Prof. Gregory concludes 

 that the last is alone adequate to explain the facts. 



In the discussion which followed, Prof. Edgeworth 

 David and Mr. T. H. Holland argued in favour of 

 Arrhenius's theory, as the cause must have been world- 

 wide, and the phenomena could not be accounted for by 

 local changes in topography. Mr. R. D. Oldham favoured 

 Prof. Chamberlain's adaptation of .Arrhenius's carbonic 

 acid theory, and pointed out the analogies between the 

 great revolutionary epochs of the earth's history, all of 

 which are associated with glacial phenomena. 



The stratigraphical papers certainly showed a bias 

 towards the Carboniferous period. No less than five papers 

 were read, dealing mainly with the faunal succession and 

 zoning of beds of this age. The recent work of Dr. 

 Wheelton Hind, Dr. Vaughan, Prof. Garwood and others, 

 as detailed in their papers, shows great strides towards 

 the completion of what, at one time, seemed a hopeless 

 problem. 



A discussion on the origin of the Trias was opened by 

 Prof. Bonney and Mr. J. Lomas. Prof. Bonney considers 

 the Bunter to be chiefly of fluviatile origin, the rivers 

 carrying the materials having their origins in Scotland, 

 the extreme north of Ireland, and another flowing from 

 the south-west. The Keuper he regards as indicating the 

 setting in of inland-sea conditions, and the Red Marl as 

 having been deposited in a great salt lake. The physical 

 and climatal conditions of the Trias were probably to some 

 extent comparable with those now existing in certain of 

 the more central parts of Asia, such as Persia or 

 Turkestan. 



Mr. Lomas compared the Triassic deposits with those 

 now forming in desert regions. He pointed out that the 

 dominant feature of deserts is concentration. The wind 

 acting on loose material concentrates particles of equal 

 size in one place, an arid climate tends to concentrate the 

 salts brought down by rivers in solution in shallow pools 

 held up by the irregular disposition of sand dunes, and 

 animal and plant life is concentrated in those regions where 

 water is more or less permanent. Taking the various 

 divisions of the Trias, he showed that In the Bunter the 

 pebble beds of the Midlands may be compared with those 

 of Lancashire and Cheshire, the only difference being that 

 the former may have been subject to the sifting action of 

 wind, which has removed the smaller sand particles, while 

 the latter has, in part, escaped this action, and has been 

 augmented by material from the south. The Upper Bunter 

 he cited as a striking example of concentration of particles 

 of even size. The Keuper shows evidence of similar sift- 



