58 



NATURE [October 7, 19 15 



illness, dealt with the shift of the western shore-line 

 in England and Wales during the Avonian period. 

 He concluded that a land mass stretching from Wales 

 to Wicklow formed a barrier during the Avonian period 

 between a "N.W. channel," reaching to the Isle of 

 Man and the Lake district, and a " S.W. channel," 

 which was an extended Bristol Channel. This barrier 

 formed the land-crest between these two channels 

 during the whole of Visdan time, and had a dominant 

 trend from Anglesey to Dudley. The whole neck of 

 land which contained the barrier and separated the 

 "channels" shifted steadily southwards as Vis^an 

 time proceeded, owing to the advance of the sea on its 

 northern side and its retreat on the south. The re- 

 markable similarity of the Vis^an sequence north and 

 south of this barrier indicated free sea communication 

 round its western margin, along which the sea re- 

 mained persistenly coastal during the period. 



Dr. Albert Jowett contributed a preliminary note 

 on the glaciation of the western slopes of the southern 

 Pennines. No striated surfaces of^solid rock had been 

 found at high levels, and for detailed information of 

 the ice-movement we had to depend on striations at 

 Salford and Fallowfield, on the distribution of drift 

 at high levels, and on the systems of drainage along 

 the edge of the ice. These indicated a general move- 

 ment from N.W.-S.E. The first barrier of hills met 

 with on approaching the Pennines from the South 

 Lancashire and Cheshire plain was almost everywhere 

 overridden with ice, which left definite deposits of 

 •drift with foreign rocks up to 1360 ft., and scattered 

 erratics up to 1400 ft. This drift had been traced 

 across the main Pennine divide near Chapel-le-Frith 

 {iioo ft.). Great lakes were held up by the ice-barrier 

 some time after it commenced to retreat from the 

 western slope of the Pennines. During early stages 

 of the retreat the drainage from the lakes in and 

 north of the Etherow valley escaped northwards, and 

 ultimately discharged through the Walsden gap into 

 the Calder. When the ice-barrier east of Manchester 

 fell below 600 ft., this drainage followed the course 

 of that south of the Etherow valley and escaped 

 southwards. 



The afternoon meeting commenced with a discussion 

 on radio-active problems in geology. Sir E. Ruther- 

 ford opened the discussion by putting the problem 

 from the point of view of the older geologists, with 

 their comparatively low estimate of the age of the 

 earth, though higher than physicists of those days 

 were inclined to concede. The discovery of radium 

 had -greatly modified the position, and the age of the 

 earth, based on evidence of radio-activity, was very 

 much higher than the estimates accepted by geologists. 

 The problem was how to reconcile geological facts 

 with these new physical determinations. Sir Ernest 

 Rutherford .was inclined to believe that the larger 

 -estimates were nearer correct than the smaller. 



Prof. J. Joly faced the problem from the viewpoint 

 of the geologist on the assumption that geologists 

 were agreed on the matter. He made several sugges- 

 tions which might have the effect of reducing the 

 large numbers derived from the study of radio-active 

 materials. 



Prof. Soddy hoped that geologists would not be in 

 any immediate hurry to decide between the geological 

 and radio-active estimates of the age of the earth. 

 Owing to the element of uncertainty about the initial 

 stages of the disintegration and the long periods in- 

 volved, there was a great terra incognita, and the new 

 theory of isotopes made it necessary to take into 

 account many possibilities not thought of a couple 

 of years ago. In addition there was always the possi- 

 bility that thorium might be a branch of the uranium 

 family, in which case some of the arguments that 



NO. 2397, VOL. 96] 



had been used entirely fell to the ground. While he 

 saw no successful method at present of altering the 

 general order of the radio-active estimate, he did not 

 regard it as more than tentative, and there might well 

 be unknown factors of sufficient importance to bring 

 the two methods into closer agreement in the future. 

 Dr. J. H. Teall, Prof. Sollas, and Dr. J. W. Evans 

 continued the discussion. 



Prof. C. A. Edwards described the results of ex- 

 periments producing twinning In metallic crystals. 

 His remarks were illustrated by an interesting series 

 of lantern slides. Dr. J. W. Evans followed with a 

 description of the different methods by which the in- 

 terference figures of a small mineral in a rock slice 

 could be kept distinct from those of the adjoining 

 minerals. He discussed various methods of using a 

 diaphragm with the Becke combination of lenses, and 

 condemned the common practice of placing the dia- 

 phragm for this purpose immediately below the 

 Bertrand lens. 



Dr. G. Hickling contributed a paper on the micro- 

 structure of coal, illustrated by a series of beautiful 

 lantern slides, showing remarkable success in dealing 

 with very difficult material. He concluded that coal 

 was essentially a "replacement" deposit consisting of 

 an original peat-like mass of vegetable ddbris, in 

 which the substance of the component tissues has been 

 largely or wholly replaced by the liquid decomposition 

 products of other vegetation. The concluding paper 

 was by Mr. Thomas Crook, describing the economic 

 mineral products of Damaraland, S.W. Africa, and 

 emphasising their value. Several research committees 

 were reappointed ; and new committees were appointed 

 to investigate rocks of Old Red Sandstone age at 

 Rhynie, Aberdeenshire, and of Lower Carboniferous 

 age at GuUane, Haddingtonshire. The sectional work 

 concluded with a field excursion to Edale and Castle- 

 ton. The surprise of the week was the magnificent 

 weather, which made a successful meeting also a 

 delightful memory. 



^ W. L. C. 



CORRESPONDING SOCIETIES AT THE 

 BRITISH ASSOCIATION. 



THE first meeting of the Conference of Delegates 

 was held on September 8, and it was announced 

 that the General Committee of the British Association 

 had altered the titles of officers of the Conference from 

 Chairman and Vice-Chairman to President and Vice- 

 President, thereby giving them the same status as 

 those of the Sections. Sir Thomas Holland delivered 

 his opening address, entitled "The Classification o* 

 Scientific Societies," which was printed in Nature of 

 September 16. 



The first subject for discussion was " Local 

 Museums," suggested by the Selborne Society, and 

 introduced by Dr. W. E. Hoyle. He laid it down 

 that the first and fundamental function of a museum 

 was to preserve. Museum officials are nowadays 

 given so much advice about the desirability of making 

 our exhibits aesthetically attractive, of compiling ex- 

 planatory labels which shall at the same time instruct 

 the specialist and interest the casual visitor, and of 

 catering for school children, that they are, he said, in 

 danger, perhaps, of forgetting that their paramount 

 duty is to see that " neither moth nor rust doth cor- 

 rupt" and that "thieves do not break through nor 

 steal." 



He gave a definition of a local museum, the first 

 duty of which, he maintained, was to preserve the 

 things of interest pertaining to the locality. Then he 

 touched upon the important and delicate question of 



